The formula
Usable quantity = Purchase quantity x Yield %
Cost per usable unit = Purchase price / Usable quantity
Portion cost = Cost per usable unit x Portion size
Why the yield step cannot be skipped: the invoice prices the product as it arrives, peel, bone and all, but the plate only carries the usable part. Dividing the pack price by the full pack weight spreads the cost over pounds that went into the bin, and every portion looks cheaper than it is. Correcting for yield first shrinks the quantity to what can really be served, raises the unit cost to the true figure, and only then does multiplying by the portion size give a cost worth pricing from.
How to use it, with an example
- Take one ingredient and the pack or case you actually buy, with the price you actually pay.
- Enter the purchase quantity in the unit you portion in, pounds for most proteins and produce, so the units line up.
- Enter the yield from your last yield test. Use 100 only for products served exactly as bought.
- Enter the portion size from the recipe spec, then read the true portion cost, the portions one purchase produces, and what the portion would have looked like costed at the plain invoice price.
- Add the menu price if you want this ingredient shown as a share of the selling price.
Worked example: A kitchen buys a 40 lb case of chicken breast for $96, which is $2.40 per lb on the invoice. After trimming, the case yields 80%, so 32 lb is usable and the true cost is $96 / 32 = $3.00 per usable lb. At an 8 oz portion (0.5 lb), the true portion cost is $1.50, and the case produces 64 portions. Costed naively at the invoice price, the same portion reads $1.20, an understatement of $0.30 a plate that repeats on every cover the case serves. The calculator above is prefilled with these same numbers, so you can compare the two costings side by side before entering your own.
Portion costs stay true only while purchase prices and yields stay current, and both drift. When ingredient costs live in the same system as the recipes that use them, a price change flows into every affected dish. That is how Odoo for Restaurants treats recipe costing: products and prices sit in Odoo Inventory, so re-costing a menu is a report, not a spreadsheet project.
Common mistakes
- Costing at the invoice price and skipping yield. Covered above because it is the biggest one: on a trimmed protein it understates the portion by 20 to 40% without a single number looking wrong. The full costing method, yield included, is set out in how to create restaurant recipes and calculate ingredient cost.
- Mixing units between pack and portion. A pack priced per pound and a portion weighed in ounces guarantees a wrong answer. Convert first: there are 16 ounces in a pound, so an 8 oz portion is 0.5 in pound units.
- Using the recipe’s theoretical portion instead of the served portion. If the spec says 6 oz and the line serves a heavy 7 oz, the true portion cost is the 7 oz figure. Weigh plated portions during a service before blaming prices.
- Costing the protein and forgetting the plate. Oil, marinade, breading, garnish and the sauce under the protein all carry cost. Cost the lead ingredient with this calculator, then build the full plate as the restaurant menu costing guide describes.
- Rounding the purchase price from memory. “About $90 a case” when the invoice says $96 moves every portion by cents that multiply across thousands of covers. Cost from the last real invoice, and re-cost when it changes, which is one of the core habits in how to reduce restaurant food cost.
- Counting portions the pack should give instead of portions it gave. A 40 lb case at 80% yield and 8 oz portions gives 64 portions, not the 80 the raw weight suggests. Planning a banquet from the raw number leaves the kitchen short.
FAQs
How is portion cost different from plate cost?
Portion cost is the cost of one ingredient’s portion on the plate. Plate cost is the sum of every ingredient portion on that plate, plus direct extras like bread service or disposables for takeout. Price the menu from the plate cost; use this calculator to build and check the ingredient lines that make it up.
What portion cost percentage of the menu price is healthy?
The plate as a whole usually needs to land at 28 to 32% of the menu price for most full-service restaurants. A single lead protein often accounts for half or more of that plate cost, so if one ingredient alone is already above 15 to 18% of the price, the plate will struggle unless the remaining ingredients are very cheap.
Should I include cooking loss in the yield figure?
Include it if your recipe portions the ingredient after cooking, for example sliced roast beef weighed at the pass. Keep prep yield and cooking yield as two labelled numbers and combine them, rather than folding them into one figure nobody can reproduce on the next test.
How often should portion costs be updated?
Every time the pack price changes, and at least monthly for your top-selling dishes. Supplier prices on proteins and dairy can move weekly, and a menu costed on last season’s prices quietly loses margin one invoice at a time. Restaurant inventory management tips covers the counting and price-check rhythm that keeps costings honest.
Why does my calculated food cost differ from my monthly food cost percentage?
This calculator gives the theoretical cost of a portion when the spec is followed exactly. The monthly figure is actual: it includes over-portioning, waste, comps and shrinkage. A persistent gap between the two is inventory variance, and it points at execution in the kitchen rather than at the costing maths.
