When to Reorder: Sell-Through Rules for a Small Beauty Retailer

17 August 2026 · The Glow Trade

A shop owner checks her bestselling sunscreen and finds the shelf empty. Again. She reorders when she notices, which is when the customer notices, which is a week too late, every time. The toner next to it tells the opposite story: fourteen units, reordered in a panic six months ago, selling one a fortnight. Both problems are the same problem: there is no number between "feels low" and the order, and the fix is two formulas that fit on an index card.

Reordering is not a feeling, it is arithmetic with your own sales data, and a small shop needs exactly three numbers per SKU to run it: how fast it sells, how long resupply takes, and how much buffer the supply risk deserves.

The short version

The reorder point is lead-time demand plus buffer: how many units sell during the resupply lead time, plus a safety stock sized by how unreliable that SKU's supply is.
Weeks of cover, stock divided by weekly sales, is the one number that tells you per SKU whether you are rich, starving or dead: under the lead time you are ordering late, over twelve weeks you are financing shelf decoration.
Sell-through per week, units sold divided by weeks on the shelf, decides the second question: which lines earn reorder at all, and which quietly leave the assortment.

The three numbers

Rate of sale first: units sold per week, averaged over a sensible window, four weeks for fast lines, twelve for slow ones. Lead time second: the real days from order to shelf, including the supplier's processing, and it is a number you measure from your own invoices, not from the website's promise. Buffer third: the judgement number, and it prices the supply risk of that specific SKU, because a hero with allocation history earns a bigger buffer than a steady toner, per the mechanics in why bestsellers go out of stock.

The reorder point falls out of them: rate of sale times lead time in weeks, plus buffer, and when stock touches that number, the order goes out. Not when the shelf looks thin, not on the monthly order day: when the number says so, which is usually earlier than instinct.

Weeks of cover, the stockroom health check

The companion metric runs the other direction: current stock divided by weekly sales, per SKU. Read it against the lead time and the assortment tells you its condition in one column. Cover below lead time means you will stock out before the resupply lands, so the order is already late. Cover of lead time plus buffer means healthy. Cover above eight to twelve weeks on a normal line means cash sleeping on the shelf, and above that it means the markdown conversation nobody wants to have.

The weekly ten-minute version of this, sorted by cover ascending, is the single highest-value habit in small-retail inventory: the top of the list is your reorder sheet, the bottom is your dead-stock warning, and both are visible before they become emergencies. The expiry clock that frames the whole exercise, because cover means nothing if the date beats the sale, is in the batch code guide.

When NOT to reorder

The second half of the discipline is the kill list, and it is harder than the triggers because every SKU arrives with a story. The rule that survives sentiment: a line with no sale in ninety days does not get reordered, and a line whose sell-through per week sits below the assortment's floor for two review cycles loses its facing to something with a pulse. Exceptions exist, and they are named: strategic traffic products, and the SKUs that complete a routine block, as the assortment logic in the first-shelf guide frames them. Everything else is a story you are paying rent on.

The one-page spreadsheet

REORDER SHEET (per SKU, updated weekly, 15 minutes)

SKU | stock | sold/wk | lead time (wks) | buffer (wks)
    | cover = stock / sold-per-wk
    | reorder point = sold/wk x (lead + buffer)
    | ACTION: stock <= reorder point -> ORDER (up to max)
              cover > 12 wks -> stop ordering, watch
              no sale in 90 days -> do not reorder, exit plan

MAX levels: hero 6-8 wks of cover, standard 4-6, tail 3-4
BUFFER guide: +1 wk steady supply, +2-3 wks allocation history
REVIEW: first Monday monthly, kill list + max levels

The bestseller special case, where the same maths runs with higher stakes and a substitution plan, has its own treatment in the overselling guide, and the benchmark frame for how fast the whole stock should turn is in the turnover article.

Questions buyers ask

My supplier's lead time swings between one and four weeks. Which number do I use?

The honest one: the worst case you have actually experienced, not the average. Averages reorder on week two of a four-week delay, which is exactly when the shelf empties. Use the longest recent lead time for hero SKUs, the realistic average for the steady tail, and revise the numbers off your own invoices every quarter, because lead times drift with seasons and with the supplier's growth. If the swing itself is the problem, that is a buffer argument for doubling the hero buffer, and a conversation worth having with the supplier, because erratic lead times are a vetting data point, per the supplier checklist.

How do I run this without inventory software?

On one spreadsheet, updated weekly from the till's sales report and a five-minute shelf count, which is exactly the sheet above. Point-of-sale systems with stock tracking automate the count, and they are worth it once the assortment passes a few hundred SKUs, but the discipline is the weekly ritual, not the tool. The shops that stock out with expensive software are the ones where nobody owns the fifteen minutes; the ones that run smoothly on paper are the ones where somebody does.

What about seasonal SKUs, where the rate of sale doubles in a month?

Seasonal lines get their own calendar logic, not the steady-state formula: the reorder decision is made before the season from last year's curve and this year's stock, because by the time the in-season rate of sale shows the spike, the lead time guarantees you miss it. The seasonal map for the category, sun care in spring, gifting in autumn, is in the seasonality guide, and the rule of thumb is that seasonal stock is bought once, ahead, with the exit markdown already priced into the margin.