Small Business Inventory Management Without Monthly Fees

Stock control that tells you what to reorder and when, built without inventory software. Includes the reorder formula most small businesses get wrong.

Published 2026-08-03 · 4 min read

Inventory software starts around thirty dollars a month and climbs steeply with product count. For a business holding a few hundred lines, most of what it provides can be built in an afternoon.

What matters is not the tool. It is getting three things right: knowing what you hold, knowing how fast it moves, and knowing when to reorder. Miss the third and you either run out or tie up cash in stock nobody wants.

What good stock control actually answers

What do we have right now? Current quantity per item.

How fast is it moving? Units sold per week. Without this, reorder points are guesswork.

When do we reorder? The point at which remaining stock will run out before a new delivery arrives.

What is not moving? Cash sitting on a shelf, which is the cost nobody puts on a report.

The structure

Sheet one — product master. One row per item: SKU, name, category, supplier, unit cost, sell price, current stock, reorder level, reorder quantity, lead time in days, location.

Sheet two — movements. One row per stock movement: date, SKU, in or out, quantity, reference, note. Every delivery in, every sale out.

Sheet three — summary. Reorder alerts, stock value, slow movers.

The movements sheet is the part people skip, and skipping it is why their stock figures drift. A number you type in is a guess. A number calculated from recorded movements is a fact.

Current stock, calculated not typed

On the product sheet:

=SUMIFS(Movements!D:D,Movements!B:B,A2,Movements!C:C,"IN")-SUMIFS(Movements!D:D,Movements!B:B,A2,Movements!C:C,"OUT")

Now stock is derived from movements. If it disagrees with a physical count, you have a recording problem to find — which is useful information rather than a number to overwrite.

Sales velocity

Units sold over the last twenty-eight days, divided by four:

=SUMIFS(Movements!D:D,Movements!B:B,A2,Movements!C:C,"OUT",Movements!A:A,">="&TODAY()-28)/4

Twenty-eight days rather than thirty gives you exactly four weeks, which avoids the distortion of counting five weekends in some months and four in others.

The reorder point most people get wrong

The common mistake is setting a fixed reorder level — reorder when we drop below twenty — without reference to how fast the item sells or how long delivery takes.

The correct calculation is:

Reorder point = (weekly velocity ÷ 7 × lead time in days) + safety buffer

As a formula, where K2 is lead time in days and M2 is weekly velocity:

=(M2/7*K2)+(M2/7*3)

That adds a three-day safety buffer. If your supplier is unreliable, widen it. If they are consistent and you are short on cash, tighten it.

This matters because two items selling at the same rate need different reorder points if one supplier delivers in two days and the other in three weeks.

Days until stockout

The number that tells you how worried to be:

=IF(M2=0,"No movement",ROUND(G2/(M2/7),0))

Where G2 is current stock. Anything under your lead time means you are already late ordering.

Two conditional formatting rules

Reorder now, red. Formula rule on the whole row:

=$G2<=$L2

Where G is current stock and L is your calculated reorder point.

Dead stock, grey. Nothing sold in ninety days:

=AND($M2=0,$G2>0)

Those two rules turn a list into a working system. You open it and the sheet tells you what needs attention.

Finding the money sitting still

Dead stock is the invisible cost. It does not appear as an expense because you already paid for it — it simply sits there as cash you cannot use.

Add a column for stock value: =G2*E2 — quantity times unit cost. Then sum the value of everything flagged as dead stock.

Most small businesses are startled by that number the first time they see it. Seeing it is what prompts the clearance sale that frees up the cash.

Counting physically, and why

Calculated stock drifts from real stock. Breakages, theft, miscounted deliveries, sales recorded against the wrong SKU.

Count everything once a quarter. Between counts, use cycle counting — count your twenty fastest-moving items every week. Those are where errors do damage, and they are a short list.

When a count disagrees with the sheet, record an adjustment movement rather than editing the stock figure. That preserves the audit trail and shows you where errors cluster.

When to buy software instead

More than about five hundred SKUs. Spreadsheet management becomes a job of its own.

Multiple locations with shared stock. Real-time sync is not a spreadsheet capability.

Barcode scanning. Worth paying for once volume is high — manual entry becomes the bottleneck and the error source.

Direct integration with your sales channel. If you sell online and stock levels must update automatically, buy the integration.

Below those thresholds, a spreadsheet built this way outperforms cheap inventory software, because it matches how your business actually works instead of forcing your business to match it.