Your actual food cost percentage is calculated with one core formula:
(Opening Stock + Purchases − Closing Stock) ÷ Food Sales × 100
That number — not what your menu spreadsheet predicts — tells you what you really spent on ingredients to generate your food revenue over a given period. To get it, you need an accurate stock take at the start and end of the period, your purchase totals in between, and your net food sales. Here's exactly how to do all three.
Pick a fixed, repeatable window. Weekly is ideal for busy kitchens; monthly is the minimum if you want numbers that mean anything. The critical rule: count at the same time, in the same way, every period. Most operators count after close on the last trading day or before open on the first, when no service is happening and deliveries aren't mid-flow.
Your closing stock for one period becomes your opening stock for the next, so you only do one physical count per period — not two.
A stock take means counting and valuing every food item you have on hand. Be systematic.
Prepare a count sheet. List every ingredient by storage location — walk-in, freezer, dry store, line, bar back. Grouping by location stops you wandering back and forth and missing items. Order the sheet to match how items physically sit on the shelf.
Count consistently. Decide your unit before you start and stick to it:
Count in pairs if you can. One person counts, one records. It's faster and cuts errors.
Don't forget hidden stock. Prep already made (stocks, sauces, portioned proteins), items in the line fridges, and anything in transit but already invoiced.
A count of items is useless until you attach money to it. Multiply each item's quantity by its current cost price — what you'd pay to replace it today, taken from your most recent invoice.
| Item | Count | Unit cost | Value |
|------|-------|-----------|-------|
| Chicken breast | 12 kg | £6.20/kg | £74.40 |
| Olive oil | 4.5 L | £5.80/L | £26.10 |
| Plum tomatoes (tin) | 22 tins | £0.95 | £20.90 |
Add every line together. That total is your stock value for the period — your closing stock figure (and next period's opening stock).
Watch your units. If you buy olive oil by the 5L case but count it in litres, make sure your cost is per litre, not per case. Mismatched units are the single biggest source of stock take errors.
Add up every food invoice for the period — everything that arrived between your opening and closing counts. Include:
Use the invoice date, not the payment date. Be careful with deliveries that land right around your count time: an item should appear in either your purchases or your closing stock count, never both, and never neither.
Pull total food sales for the same period from your POS. Use the net figure — sales excluding VAT/sales tax — and keep it to food only. If you sell drinks, separate those out; mixing them distorts your food cost percentage badly because beverage margins are completely different.
Now you have everything. Plug it in:
Cost of goods sold (COGS) = Opening Stock + Purchases − Closing Stock
Food Cost % = COGS ÷ Net Food Sales × 100
COGS = 8,000 + 22,000 − 7,000 = £23,000
Food Cost % = 23,000 ÷ 85,000 × 100 = 27.1%
So you spent 27.1p on ingredients for every £1 of food you sold.
Most full-service restaurants target 28–35%. The "right" number depends entirely on your concept — a high-volume pasta spot runs lower; a steakhouse or seafood restaurant runs higher because the raw product costs more. Set your own target based on your menu pricing, then track movement over time. The trend matters more than any benchmark.
The number above is your actual food cost — what genuinely left your stock. Your theoretical food cost is what your recipes say you should have spent, based on perfect portions and zero waste.
The difference between them is pure leakage:
If your theoretical food cost is 27% but your actual is 33%, that 6-point gap is money walking out the door — and a stock take is the only way to see it. Chase that gap, not the headline number.
A stock take only earns its keep when you do it consistently and actually read the results. Count the same way every period, track your food cost percentage on a simple chart, and investigate any swing of more than a point or two. Over a few cycles you'll spot exactly which dishes, suppliers, or shifts are eating your margin.
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If keeping ingredient costs current, portion math accurate, and recipes properly costed is the part that always slips, that's exactly what we're building PrepSheet for — it turns any recipe into a costed, scalable prep sheet so your theoretical numbers stay honest between stock takes. If that sounds useful, you're welcome to [join the waitlist](#).