How to cost a recipe
A recipe card has three columns: quantity, price, loss. The first two make an addition; the third makes it a real cost — and it is the one people forget.
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The formula
For each ingredient: net quantity × purchase price ÷ (1 − loss). Add the lines up, then divide by the number of portions if the recipe makes several. The result is a food cost: no labour and no energy, which are managed at the level of the P&L and cannot be split dish by dish in any reliable way.
The quantity is what reaches the plate, after trimming, peeling or cooking. The price is the one on the latest invoice, in the same unit: kilos with a price per kilo, grams with a price per gram — never one with the other. Mixing them is the most common mistake, and it goes unnoticed because the result stays plausible.
Worked example: beef, crushed potatoes
One portion sold at €24.00 including VAT, or €21.82 net at the French 10% rate.
| Beef — 180 g net at €20.00/kg, 25% loss (trimming and cooking) | €4.80 |
|---|---|
| Potatoes — 250 g at €1.20/kg, 20% peeling loss | €0.37 |
| Butter — 20 g at €10.00/kg, no loss | €0.20 |
| Real cost of the portion | €5.38 · 24.6% of the net price |
| The same dish with losses left out | €4.10 · 18.8% |
| Multiplying by (1 + loss) | €5.06 |
Without losses, the dish appears to cost 18.8% of its price instead of 24.6%. At 40 portions a week, the €1.28 gap per plate comes to €2,652 over a year — margin you think you have and do not.
Why loss divides
To serve one net kilo of a product that loses a quarter in trimming, you have to buy 1 ÷ 0.75, or 1.33 kg. Multiplying by (1 + loss) would give 1.25 kg: multiplying always understates, and the gap widens as the loss grows. Trimming at 50 % doubles the cost of the ingredient; it does not add half.
Some orders of magnitude: trimming a cut of beef 10 to 20 %, peeling vegetables 15 to 30 %, cooking meat 20 to 30 %, filleting a whole fish 40 to 60 %. A fish dish costed without yield is out by half.
A card that is right in January is wrong by June
A recipe's cost follows the purchase price, which moves with every delivery. A card typed once keeps calculating with the prices of the day it was written. That is what Margéo automates: every invoice it reads updates the cost of every recipe that uses the product, and flags the dishes whose selling price no longer keeps up.