How to read a WSSI, week by week

Read across the weeks, not down a column

The most common reading error is treating the WSSI as this week’s position report. Reading down a column answers “where am I” — this week’s sales, this week’s stock, this week’s cover. But the stock report already answered that, more accurately and hours earlier. Reading across the cover row answers “where am I going to be”, which is the only question the grid was built for, and the only one you can still do anything about.

That distinction matters more than it sounds, because the WSSI is a forecast instrument wearing a report’s clothing. Its columns look like history and most of them are not. Every cell to the right of the current week is an assumption — an assumed rate of sale multiplied out, and an assumed receipt date that somebody set months ago and may not have looked at since. Read it as history and you will nod at a row of numbers. Read it as a forecast and you are looking at a set of claims, each of which can be tested and some of which can be changed.

The practical consequence is about deadlines. A column read produces observations. A row read produces decisions with a clock attached, because every fix has its own lead time: rephasing a receipt needs supplier agreement and a shipping slot, redistributing stock between doors or channels needs a pick and a transit, cancelling needs to happen before the order is committed to production. If cover breaks down in week nine and you find it in week eight, you have one lever left and it is the expensive one. Find it in week four and you have all of them. The row read is what tells you how many weeks of runway you have to apply a fix — and runway, not severity, is what decides which fix is available.

So the read hunts for two weeks specifically. The first is the week the plan runs short — where cover drops under the time it takes to get more sellable stock in. The second is the week the plan piles up — where cover rises past the number of trading weeks left to sell it. Everything else in the grid is either evidence for one of those two, or it is context. The rest of this guide finds both on a worked example.

A WSSI to read

Say a category plans a 12-week window in units. It opens on 6,000 units, plans 14,050 units of sales across the window, and plans 9,000 units of intake in four receipts — weeks 2, 4, 6 and 8 — landing it on 950 units of carryout at week 12. Six weeks have traded, six are left, and one receipt is still open. That is the state most WSSI reads actually happen in.

Illustrative figures only — a hypothetical category, not a benchmark and not a real brand. Cover here is computed on a forward four-week average of planned weekly sales, truncated to the weeks remaining at the end of the window, so week 4’s cover divides week 4’s closing stock by the average of weeks 5 to 8 while week 10’s divides by the average of weeks 11 and 12. Actuals stop at week 6. To run the single-period arithmetic on your own numbers, use the WSSI calculator; for a structured worksheet, the WSSI template.

Start with the cover line

Cover is the first line you read because it is the only line that already contains a judgement. Stock value is never a signal on its own — 7,490 units is neither good nor bad, and any instinct that it is “high” is smuggling in an unstated rate of sale. Divide it by the rate at which it will actually leave and you get a number you can act on. That is why the read starts on the bottom row and works up.

There are three distinct reads available off that one row, and they do different work. The first is absolute: cover against your replenishment floor, meaning how many weeks you could trade with no receipt at all before the shelf runs thin. The second is directional: the trend across weeks, which almost always beats the level, because a cover figure of four rising is a different problem from a cover figure of four falling and the level alone cannot tell you which you have. The third is structural: cover against the phasing shape the season was supposed to have.

That third read is the one teams skip, and it is where the expensive mistakes hide. Cover should not be flat — it should build into peak and fall toward the exit. A season has a shape: you want depth in front of the weeks that sell hardest and you want to be running out deliberately as the window closes, because the alternative to running out at the exit is carrying stock into a market that has stopped paying full price for it. A flat cover line across a whole season is usually a plan built off an average rather than phased to demand, and its defining property is that it reads acceptable every single week — right up until the season ends heavy. There is no universal right level; the benchmark ranges are directional at best, and the lead time and window length in front of you matter more than any published figure.

Walk the actual cover row in the grid: 4.7, 5.9, 4.6, 3.6, 4.4, 5.3. Three inflections are worth naming before diagnosing any of them. Week 2 jumps to 5.9 because a 3,000-unit receipt landed into a week selling 880 — that is a phasing observation, not yet a problem. Week 4 falls to 3.6, the lowest point in the traded weeks and well under the 5.0 the plan expected there. And week 6 turns back up to 5.3 while the forward rate of sale is running under plan, which is the shape that precedes trouble rather than the shape that reports it. The next two sections take week 4 and week 6 in turn.

Finding the stock-out week

The stock-out week is the first week cover falls below your replenishment floor — and the floor is a real number from your supply chain, not a round one from habit. It is the time it takes to get more sellable stock onto the floor or into the fulfilment centre: order to receipt if you are chasing, transit and processing if you are pulling from a hub, pick and ship if you are rebalancing between doors. Whatever that duration is, cover below it means a week where demand exists and stock does not, and nothing you decide on the day will change it.

In the grid that week is week 4. Cover reads 3.6 against a plan of 5.0, and the cause is unambiguous once you read up the column rather than across: the planned 2,500-unit receipt shows zero on the intake actual row. Sales were fine — week 4 traded 950 against a plan of 1,100, softer but not collapsing. The entire 1.4 weeks of cover that went missing went missing because a receipt did not land.

Here is the operator point that justifies the weekly cadence: this stock-out has already happened, and a monthly report would have netted it away. The receipt arrived in week 5, cover recovered to 4.4, and by the time the month closed the position looked entirely normal. The lost week is invisible at monthly granularity because the month contains its own correction. The WSSI catches it for one reason only — the week is the unit, and a week is short enough that a slip cannot hide inside it.

The harder version of this read is the one that has no dip at all. Aggregate closing stock going positive-but-small hides a stock-out, because category-level stock is not sellable stock. A category holding four weeks of cover can be out of its core sizes, out of the colour that was doing half the volume, or out at a third of its doors while a warehouse holds the balance. The cover figure is an average over a population that has stopped being uniform, and averages are exactly the wrong instrument for a distribution that has broken. If the cover line looks calm while sell-through is stalling, the fragmentation is where to look — see size curve for the size dimension and allocation for the door dimension.

A stock-out week that sits in front of you rather than behind you is a reorder question, and it is a question with a deadline set by lead time rather than by the calendar. That decision has its own arithmetic — how much of the season is left to sell into, what sell-through already tells you, and how much of the budget was deliberately held back — and it is covered separately in reading sell-through before it is too late. The job of the WSSI read is narrower: find the week, and find it while the answer is still a chase rather than an apology.

Finding the overstock week

The overstock week is the first week weeks of cover exceeds the trading weeks left in the selling window. The logic is arithmetic rather than opinion: from that week onward the plan holds more stock than the remaining window can absorb at full price, so some portion of it will still be there when the window closes. You do not need a view on the market to establish that. You need two numbers that are already on the grid.

On the original plan the grid looks safe. Week 6 closes at 7,490 units, cover reads 5.3, and six trading weeks remain — comfortably inside the window. But the plan is no longer the right divisor. Six weeks have traded 11% under plan, and if you carry that through, the forward rate of sale is about 1,268 a week rather than the planned 1,425. The same closing stock is then 5.9 weeks against 6 — no longer comfortable, exactly borderline. And there is still a 1,500-unit receipt scheduled into week 8 that nobody has re-examined since the plan was written. Add it and the position goes clearly over.

So the overstock week is week 8, and the thing to notice is what created it. The overstock week is almost always a receipt decision, made months ago, that the current rate of sale no longer supports. Nothing has gone wrong in week 8. Nothing has happened in week 8 at all. It is a week that only becomes a problem because a commitment made under one demand assumption is still pointing at a plan that is now trading under a different one, and no step in the normal weekly routine forces anyone to check the two against each other.

Once you have found the week, split the diagnosis, because the two causes need opposite responses. Intake-driven overstock is a receipt landing into a week that no longer needs it — the stock line jumps on a receipt week while the sales line is broadly holding. That is fixable by rephasing, and it is fixable cheaply if you find it before the goods ship. Sales-driven overstock is a falling rate of sale inflating cover with nothing moving on the stock line at all — the closing stock is roughly where it should be and the cover figure rises anyway, because the divisor shrank. Rephasing will not fix that one; the excess is real and the only question is how you clear it.

You tell them apart by reading which row moved, which is why intake actual belongs on the grid rather than in a separate receipts file. For the underlying ratios, the weeks-of-supply calculator and the stock-to-sales ratio calculator will run a single week for you.

Phasing intake: the only row you can still move

Of the three lines on a WSSI, only one has a live decision attached to it. Sales are read — you can influence them at the margin but you cannot set them. Stock is derived — it is the arithmetic consequence of the other two and has no independent existence. Intake is chosen. Every future cell on the intake row is a decision somebody made and, for as long as the goods have not shipped, a decision somebody can still unmake. That is why the intake row is where a WSSI read turns into an action.

The reading test is a single question: does each receipt lead the demand it supports by enough time to be sellable when that demand arrives? Not “is it in the right month” — the right month is not a unit of trade. Enough time means landed, processed, allocated and on the floor before the weeks it was bought for start selling.

Three phasing failures are visible on the row itself, without needing any other system. The first is front-loading: most of the intake landing in the opening weeks, which is a plan built around the shipping calendar rather than the demand curve, and which produces exactly the sawtooth the worked grid shows at week 2 — a 3,000-unit receipt into a week selling 880. The second is intake landing after the peak it was bought for, the most expensive failure of the three, because that stock has skipped its full-price window entirely and will be sold against a curve that is already declining. The third is evenly-spaced receipts against a curved sales line — monthly deliveries of similar size into a season that sells nothing like evenly, which guarantees both a thin week and a heavy one and is usually a vendor convenience that nobody ever revisited.

Three actions are available, and their costs differ sharply. Pulling a receipt forward needs supplier co-operation, sometimes a freight upgrade, and cash earlier than you planned to spend it. Pushing a receipt back is the cheapest lever on the board — but it is only available on goods that have not shipped, which is a shrinking set. Cancelling is available for a narrow window, is rarely free, and usually costs relationship as well as money. The movable share of intake shrinks every week, so a WSSI read that happens late is a read with fewer options, not just a late one. This is the strongest argument for the weekly cadence and it has nothing to do with information: the information is barely different a week later, but the menu is.

How much intake is movable at all is governed upstream by the buying budget — what is still uncommitted, what is on order, and what the plan has already spent. That is a different view of the same inventory, and it has its own guide: how to set open-to-buy, with the open-to-buy calculator for the arithmetic. For how the budget view and the weekly view relate to each other — which to reach for, and when — see OTB vs WSSI. That comparison is deliberately not made here.

Reading actuals against plan

There are three variances on a WSSI and they should be read in a fixed order: sales variance first, intake variance second, closing-stock variance last. Sales variance is the one everybody reads. Intake variance — units actually received against units planned to be received — is the one teams routinely skip, usually because receipts live in a different system from the plan and reconciling them is somebody else’s job. Closing-stock variance is the one that gets reacted to, and it is the one that should be trusted least on its own.

A closing-stock variance is almost never a stock problem — it is the accumulated residue of the other two, so decompose it before reacting to it. The worked grid makes the point cleanly. At week 4, closing stock is 5,420 against a plan of 7,550: 2,130 units light. Read alone, that is alarming, and it is the kind of number that gets escalated as a demand collapse. Decomposed, it is two facts pulling in opposite directions. Cumulative intake is 2,500 units short, because week 4’s receipt did not arrive. Cumulative sales are 370 units short, which on its own would have left stock 370 units heavier, not lighter. Minus 2,500 plus 370 is minus 2,130 — the whole variance, and none of it is a stock decision. One number, two causes, and two completely different actions: chase the receipt, and watch the sales trend.

The second discipline is separating noise from trend. A single week 5% under plan is noise, and treating it as signal is how plans get rewritten every seven days until they mean nothing. Six consecutive weeks in the same direction totalling 11% under is a trend, and it is a trend the WSSI surfaced weeks before a monthly close would have shown anything more than a soft month. The test is not the size of any one week — it is direction and persistence. The sell-through calculator gives you the same read from the other side, and the retail math formulas reference has the underlying definitions if you need to standardise how variance is calculated across a team.

The third point is the one with teeth. The moment a trend is established, the forward plan is the number that has to change — not the commentary, not the flag on the exception report, the plan. Until the forward sales line is revised, every cover figure to the right of today is calculated against demand you have already stopped believing in, and the grid will keep telling you a story you have privately rejected. Reforecasting is not an admission that the plan was wrong; it is what makes the next six weeks of the grid readable at all.

Reading this year against last year

Last year is the sanity check on the plan itself, not just on how you are trading against it. Plan-versus-actual tells you whether you are hitting the number you set; last year tells you whether the number you set had a defensible shape. Three rules make the comparison worth doing.

First, compare trading week to trading week, never calendar date. The retail calendar, 4-5-4 period boundaries, moving holidays and the occasional 53rd week will all silently misalign a date-matched comparison, and the variance that falls out of the misalignment is indistinguishable from a real one at a glance. A date-matched read manufactures variances that do not exist, and then somebody acts on them.

Second, read last year as a shape check on phasing rather than as a target. Overlay last year’s cover line on this year’s and the useful information is where the two peak and where they fall away, not whether this week is up or down. If last year’s cover peaked two weeks earlier than this year’s plan does, that gap should be a decision somebody made and can explain — a later launch, a changed delivery, a deliberate move away from a promotion that did not pay. If nobody can explain it, it is not a decision, it is a discovery, and week six is a poor time to make it.

Third — the caveat most teams miss — last year’s sales are a record of what you had, not of what customers wanted. Every week you were out of stock last year is a week whose sales figure understates real demand, sometimes badly. Plan to those weeks and you rebuild the same shortage, then compare favourably against it and conclude the plan worked. If you know which weeks were broken, either exclude them or lift them deliberately; if you do not know, treat the whole comparison as directional and say so out loud.

There is also a point at which last year stops being useful at all. A relaunched category, a repriced range, a materially changed door count or channel mix, a shifted delivery cadence — any of these breaks the comparison, and forcing it produces confident nonsense with a variance percentage attached. When the comparison is broken, say it is broken and read the plan against the forward rate of sale instead. That is a weaker read, but it is an honest one.

What to do when cover trends up

A rising cover line is the most common finding in a weekly read and the one most often mishandled, because the instinctive response — promote out of it — is the last item on the list rather than the first. The levers have an order, and the order is by margin cost.

One: move or cancel intake that has not shipped. Cheapest by a wide margin, and the only lever that gets cheaper the earlier you pull it. A receipt pushed two weeks costs a conversation; the same receipt landed and then marked down costs margin on every unit. This is the lever the overstock-week read exists to enable, and it is the reason the read has to happen before the goods are on the water rather than after they are in the building.

Two: redistribute what you already own. Cover is an average over a population, and where the average is high the distribution is usually uneven — some doors, channels or sizes are thin while others are heavy. Moving stock toward the thin end costs a pick and a transit and gives away no price at all. See allocation and replenishment for how the two mechanisms differ.

Three: hold and trade through. Legitimate, and badly under-used. Not every rising cover line is a problem — cover building in front of a peak is the plan working exactly as intended, and cutting into it because a threshold went amber is how teams engineer their own stock-out in the weeks that mattered most. The test is whether the build is intentional and whether the demand it is built for is still expected. If both are true, the correct action is to do nothing and say so.

Four: markdown. Last, because it is the only lever that pays for the correction directly out of margin. Once cover exceeds the trading weeks left in the window, the excess clears at a discount whatever you decide, so the only variable left is how early and how shallow. The arithmetic of depth and timing, and the upstream argument that most markdowns are decided long before anyone reaches for one, both sit elsewhere: see how to control markdowns before the season starts and the markdown calculator, or the markdown definition for the mechanics.

Stated plainly, the decision variable for the whole ladder is one comparison: weeks of cover against trading weeks remaining, checked every week. While cover sits under the weeks left, you are trading a position. Once it sits above, you are managing an excess, and the levers you have left are strictly a function of how early you noticed.

When the WSSI is lying to you

Every read above assumes the grid is telling the truth. Often it is not — not because anyone falsified it, but because a WSSI is built from inputs that decay at different rates and it goes on rendering a clean, confident number long after one of them has gone stale. Five conditions produce a grid that reads healthy and is not.

Stale intake dates. The intake row is a forecast, not a fact, and it is the input most likely to be wrong. One receipt that has already slipped and has not been re-dated makes every downstream closing-stock cell and every downstream cover figure wrong — not approximately wrong, structurally wrong, because closing stock carries forward and the error compounds week over week. This is the single most common cause of a WSSI that looks fine, and it is invisible from inside the grid: the arithmetic is flawless, the input is fiction.

Aggregation. Category-level cover conceals size, colour and door-level brokenness. Four weeks of cover at category level can sit alongside a core size that has been out for two weeks and a hero option that has been out for three, with the balance held in sizes and options nobody is asking for. The higher the level you read at, the more reassuring the number and the less it means.

Returns and cancellations not netted. If gross sales feed the grid, sales are overstated and cover is understated — you look leaner than you are, in exactly the direction that encourages more buying. High-return categories and channels distort this badly enough that a gross-fed WSSI can point the wrong way on the overstock question entirely.

Cover computed on a decaying rate of sale. This is the forward-versus-trailing choice from the definition above, and here is where it gets paid. A trailing average flatters a line at the end of its curve: the last four weeks were strong, the divisor stays high, cover reads low, and the grid quietly recommends buying more of something whose demand is already falling away. The flattery is worst exactly when it is most expensive. If cover is computed on trailing sales anywhere in your grid, know it, and discount the reading on any line past its peak.

A plan nobody has reforecast. Reading actuals against a pre-season plan that has not been revised measures variance against fiction, and does it with total precision. Six weeks into a trend, the plan column has stopped being a forecast and become a historical artefact of what the team believed in a room in March. The WSSI is only ever as honest as its intake row and its forward sales assumption.

There is a practical test that costs nothing. Before you trust a cover figure enough to act on it, ask two questions: when were the intake dates last confirmed against what the vendors and the purchase orders actually say, and when was the forward sales line last revised. If either answer is “at the start of the season”, you are not reading a plan. You are reading a document.

Running the weekly read

The WSSI read is a meeting that produces decisions, not a report that gets circulated. Run it in the order this guide is written in: cover line first, then the two exception weeks, then the intake decisions those weeks force, then actions with an owner and a date against each. Explanation and commentary fill whatever time is left, which is the correct amount of time for them.

Hold it on the same day every week. That is not administrative tidiness — it is what makes the comparison like-for-like. A read pulled on a Tuesday one week and a Friday the next contains a different number of trading days, and the trend you think you are seeing is partly an artefact of when somebody happened to pull the data. Fixing the day removes a variance you would otherwise spend time explaining.

What keeps the meeting short is pre-flagging rather than walking every line. If the exception weeks are already marked before anyone sits down, the discussion starts at the decision. If they are not, the meeting becomes a group read-through and the decisions get made in the last four minutes by whoever is still talking. A WSSI read that ends without a receipt being moved, held or cancelled was a status update. That is not always wrong — some weeks the correct decision genuinely is to hold — but it should be a stated decision with a reason, not a default that nobody noticed.

For a structured 13-week worksheet to run the cadence in, use the WSSI template; for a single-period check between reads, the WSSI calculator.

Where the read breaks down

Everything above rests on two assumptions: that the intake row reflects current receipt dates, and that the forward sales line reflects current trade. Neither is exotic. Both are maintained by hand in a spreadsheet WSSI — in a file that sits apart from the receipts, the purchase orders and the vendor confirmations that actually determine them. So the assumptions do not fail loudly. They degrade quietly between reads, and the first symptom is a cover figure that has been wrong for a fortnight while the meeting kept treating it as fact.

That is the practical case for a connected workflow rather than a better spreadsheet. When the weekly stock position, the receipts and the purchase orders sit on a single data model, a slipped delivery re-dates the intake row on its own and the cover line moves the same day, rather than at the next manual refresh. The read stops being an exercise in verifying inputs and becomes what it should be — deciding what to do about them. That is the whole argument for keeping plan, buy and allocate in one place: not that the arithmetic gets easier, but that the inputs stop going stale in the gaps between people.

• ✓Read across the weeks, not down a column — cover line first, explanation last. A column read gives observations; a row read gives decisions with a deadline.
• ✓The stock-out week is where cover breaches your replenishment floor; the overstock week is where cover exceeds the trading weeks left in the window.
• ✓Intake is the only row you can still move, and the movable share shrinks every week — a late read has fewer options, not just later ones.
• ✓Decompose a closing-stock variance into sales variance and intake variance before reacting to it; it is almost never a stock problem on its own.
• ✓Trust the grid only as far as its intake dates and its forward sales assumption are current — everything else in it is arithmetic on those two inputs.

• Project closing stock and cover with the WSSI calculator →
• Download the free WSSI template (13-week worksheet) →
• What a WSSI is — the three lines and the formula →
• OTB vs WSSI — how the budget and the weekly view relate →
• Weeks of supply calculator — cover for a single period →

Frequently asked questions

How do you read a WSSI?

Read across the weeks, not down a single column. Start with the weeks-of-cover line and follow it forward to find the first week cover falls below your replenishment floor and the first week it rises above the number of trading weeks left in the selling window. Then read the intake row to see which receipts you can still move, and only after that read sales and intake actuals against plan to explain why the cover line moved. Explanation comes last, because the decisions sit in the cover and intake rows.

What is a good weeks of cover on a WSSI?

There is no universal number — the right cover depends on the replenishment lead time, the length of the selling window, and where the week sits in the season’s phasing. The useful test is relative rather than absolute: cover should be highest going into peak trade and falling steadily toward the season exit. A cover line that stays flat across a whole season is usually a sign the plan was built off an average rather than phased to demand, and it will read acceptable every week until the season ends heavy.

How do you spot an overstock week on a WSSI?

Find the first week where weeks of cover exceeds the number of trading weeks left in the selling window. From that week onward the plan holds more stock than the window can sell at full price. Then check which row caused it: a receipt landing into a week that no longer needs it is an intake problem you can fix by rephasing or cancelling, while a falling rate of sale inflating cover with nothing moving on the stock line is a demand problem that rephasing will not fix.

How do you read a WSSI against last year?

Compare trading week to trading week rather than calendar date, so the retail calendar, period boundaries, moving holidays and any 53rd week line up — a date-matched comparison manufactures variances that do not exist. Read last year as a shape check on your phasing rather than as a target: if last year’s cover peaked two weeks earlier than your plan does, that difference should be a decision rather than a discovery. And treat last year’s sales as contaminated in any week you were out of stock, because those weeks record what you had rather than what customers wanted.

What should you do when weeks of cover keeps trending up?

Work the cheapest lever first. Move or cancel intake that has not shipped; then redistribute stock to the channels, doors or sizes where cover is thin; then decide whether the build is intentional pre-peak cover you should simply trade through. Markdown is the last lever, not the first. The decision variable is straightforward: once cover exceeds the trading weeks left in the window, the excess will clear at a discount regardless, so acting early and shallow costs less margin than acting late and deep.

When can you not trust a WSSI?

When the intake row is stale, when the read is too aggregated, or when the plan behind it has not been reforecast. Intake is a forecast rather than a fact, so a single receipt that has already slipped makes every downstream closing-stock and cover cell wrong. Aggregated cover hides brokenness — a category can show four weeks of cover while its core sizes have been out for two weeks. And reading actuals against a pre-season plan nobody has revised measures variance against fiction, precisely.