The portion-cost formula starts with usable units
Use one unit system throughout the recipe. Grams and millilitres make pack conversions clear.
Add all ingredient lines, sub-recipes, garnish and packaging. If you cost a batch, divide its total by the number of saleable portions the batch actually yields.
A £6.80 chicken pack becomes £3.47 on one finished plate
The following Riverside Kitchen chicken bowl is illustrative. Prices are ex-VAT where the restaurant can recover input VAT. Use the accounting basis your adviser confirms.
Metro Poultry invoices a 1kg pack of boneless chicken thigh at £6.80. A kitchen test produces 850g after trimming and cooking.
A plate uses 180g of cooked chicken.
The rest of the plate costs:
- Rice: £0.32.
- Roasted vegetables: £0.58.
- House sauce: £0.41.
- Pickled garnish: £0.17.
- Takeaway bowl, lid and label: £0.55.
Ignoring the chicken yield would cost it at £1.22. The whole plate would appear to cost £3.25, understating one portion by £0.22. At 900 portions a month, that hidden difference is £198.
A supplier case must be converted before the recipe can use it
Invoice descriptions rarely match kitchen quantities. A case may contain 6 × 2.5kg rice bags. A sauce may arrive as 4 × 3 litres. A garnish may be priced per 250g tub.
For a rice case costing £24.00:
If the recipe uses 200g of cooked rice, do not multiply that by the raw-rice unit cost. Run a batch yield test. Suppose 1kg dry rice produces 2.8kg cooked rice.
Cost the full rice sub-recipe and divide by its measured portions. Do not mix bought weight with cooked serving weight.
Sub-recipes stop sauces and garnishes disappearing from the plate
A house sauce used across four dishes needs its own cost card. Add oil, herbs, spices, lemon, salt and the yield of the finished batch.
Suppose one sauce batch costs £16.40 and produces 8,000ml after reduction and transfer loss.
A 200ml portion would cost £0.41. If service actually ladles 230ml, it costs about £0.47. That extra £0.06 belongs in the theoretical-versus-actual variance, not inside the standard recipe.
Cost visible garnish too. A £0.17 garnish used on 900 dishes is £153 a month. “A little” is still a quantity.
Current invoice prices keep the recipe from becoming confidently wrong
A portion card is a snapshot. Supplier prices, case formats and substitutes change.
Involiqo item analytics can place a recurring invoice line beside its previous unit price and pack description. That helps the operator see whether the chicken moved from £6.80/kg to £7.30/kg, or whether a case now contains fewer units.
At £7.30/kg and the same 85% yield, the 180g chicken portion becomes:
The bowl rises from £3.47 to £3.58 before any other line changes. The operator still confirms supplier credits, substitutions, recipe mapping and whether the observed yield remains valid.
Yield tests must use saleable output, not optimistic scraps
Weigh the ingredient as purchased. Prepare it using the normal kitchen specification. Weigh what is genuinely saleable in the recipe. Record trim, cooking loss and any usable by-product separately.
Do not count bones as zero-cost stock merely because they go into a sauce. Credit them only through a consistently costed sub-recipe. Do not use one unusually clean pack as the permanent yield.
Repeat the test when the supplier, cut, size or preparation method changes. Three normal tests provide a more useful working average than one perfect result.
WRAP reported in November 2024 that UK hospitality and food service throws away 1.1 million tonnes of food a year. It said 75% could have been eaten. In February 2023, WRAP also reported that 48% of diners who left food cited portion size, with almost 15% of main courses left uneaten on average.
Those sector figures do not set your recipe yield. They show why your own scale data matters.
Portion cost is not the same as menu profitability
The £3.47 is the ingredient and packaging cost of one bowl. It does not include kitchen labour, front-of-house labour, rent, rates, utilities, card fees, delivery commission, depreciation or finance costs.
Use the UK food-cost method at https://involiqo.com/blog/food-cost-percentage-formula-uk, the variance bridge at https://involiqo.com/blog/theoretical-vs-actual-food-cost and the net-margin guide at https://involiqo.com/blog/uk-restaurant-net-profit-margin before treating food GP as final profit.
At a £12.00 ex-VAT selling price, the bowl's theoretical food and packaging cost is:
That percentage is a menu check, not proof that the dish covers every restaurant cost.
Frequently asked questions
Should recipe costing include labour?
Keep direct ingredient and packaging cost visible as the standard portion cost. Then add labour or contribution measures separately if your decision needs them. Mixing a rough labour allowance into some recipes but not others makes comparisons unreliable. Use one documented approach across the menu and reconcile it with the full profit and loss statement.
How often should a restaurant update portion costs?
Refresh high-value and volatile items when a current invoice changes. Review the complete recipe after a supplier, pack, yield, portion or preparation change. Run a scheduled monthly check for core lines and a full menu review before repricing. Record the price date so an old cost cannot look current.
Do you cost trim if it is used elsewhere?
Yes, but avoid charging the same purchase twice. Allocate usable trim to a documented sub-recipe or by-product credit. The main recipe should carry only its share of the purchased cost. If trim is discarded, its cost stays in the edible-yield calculation for the original ingredient.
Key takeaways
- Convert supplier packs into grams, millilitres or items.
- Divide by measured usable yield, not catalogue weight.
- Cost sub-recipes, garnish and packaging.
- Divide batches by saleable portions actually produced.
- Refresh important lines from current supplier invoices.
Sources
- Vancouver Community College, Culinary Math: https://library.vcc.ca/media/vcc-library/content-assets/learning-centre/worksheets/by-coursex2fprogram/business/CulinaryMath-RecipeCosting.pdf
- WRAP, 4 November 2024: https://www.wrap.ngo/media-centre/press-releases/wrap-urges-hospitality-and-food-service-ceos-and-leaders-take-stand
- WRAP, 23 February 2023: https://www.wrap.ngo/media-centre/press-releases/portion-size-main-reason-plate-waste-when-we-eat-out
Weigh one recipe this Monday
Choose one high-volume dish. Copy the latest invoice prices, weigh the purchased and saleable ingredients, cost every sub-recipe and compare the measured portion with the recipe card.
See how Involiqo connects supplier invoice lines with item-level cost evidence at https://involiqo.com/#bento-overview.
See it in practice
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