Stacks of supplier invoices pile up, but most restaurant owners never connect them to actual dish costs. Here's how to turn those invoices into precise cost prices that protect your margins.
A local bistro owner discovered their signature burger was losing €1.20 per plate after properly calculating ingredient costs from invoices. Most restaurant owners collect invoices religiously but never translate them into actual dish costs. Without this step, you're flying blind on profitability.
Collect every supplier invoice from the past month
Round up all invoices from every supplier. Don't just grab the obvious ones:
- Primary food distributor
- Local produce vendor
- Meat or seafood specialist
- Beverage supplier
- Specialty items (imported cheeses, exotic spices)
- Packaging that touches food
⚠️ Note:
That emergency supermarket run for fresh herbs? It counts. Those €3.50 purchases add up faster than you think.
Extract unit prices from each invoice line
Go through every invoice and record:
- Exact product description
- Package size (per kg, per case, per piece)
- Net price (excluding VAT)
- Cost per kilogram or individual unit
💡 Invoice breakdown example:
Your supplier invoice shows:
- Prime ribeye, vacuum-packed, 3.2 kg for €89.60 excl. VAT
- Unit cost: €28.00 per kilo
- Fresh scallops, 500g tray for €18.75 excl. VAT
- Unit cost: €37.50 per kilo
Measure exact portions for each dish
Here's where precision matters most. You need to know exactly how much of each ingredient goes into every dish. That means weighing:
- Protein portions down to the gram
- Vegetable sides and garnishes
- Sauce quantities per serving
- Cooking fats and oils used
💡 Portion costing example:
Pan-seared salmon with risotto:
- Salmon fillet 180g: €24.50/kg = €4.41
- Arborio rice 75g: €4.20/kg = €0.32
- Mixed vegetables 60g: €6.80/kg = €0.41
- White wine 25ml: €8.50/liter = €0.21
- Olive oil 8g: €15.00/kg = €0.12
Total ingredient cost: €5.47
Account for prep waste and trimming losses
Raw ingredients don't magically become perfect portions. Every product has unavoidable waste that inflates your real costs:
- Whole fish → clean fillets: 40-50% loss
- Whole poultry → usable meat: 25% loss
- Fresh greens → salad-ready: 20% loss
- Root vegetables → peeled/trimmed: 15% loss
The real cost formula: Invoice price ÷ (100% - waste%)
💡 Waste calculation example:
Whole sea bass at €16.50 per kilo:
- Processing waste: 42% (head, bones, scales, fins)
- Usable flesh: 58%
- True fillet cost: €16.50 ÷ 0.58 = €28.45/kg
You're actually paying €28.45 for each kilo of fish that reaches the plate.
Recalculate costs monthly without fail
Supplier prices shift constantly. But here's the kind of thing you only learn after closing your first month at a loss: even small price bumps compound into serious margin erosion if you don't track them.
- Scan new invoices for price changes
- Update your cost calculations immediately
- Adjust menu prices before margins disappear
⚠️ Note:
A 12% ingredient cost increase pushes your food cost from 28% to 31.4%. On a €25 dish, that's €0.85 less profit per plate.
Verify your food cost percentage per dish
Now you can see if each dish actually makes money. Use this calculation:
Food cost % = (Ingredient cost ÷ Menu price excl. VAT) × 100
💡 Food cost verification:
Your salmon dish costing €5.47:
- Menu price: €28.50 incl. 9% VAT
- Net price: €28.50 ÷ 1.09 = €26.15
- Food cost: (€5.47 ÷ €26.15) × 100 = 20.9%
Excellent food cost ratio for a premium fish dish.
Converting invoices to cost prices (step by step)
Gather all invoices from the past month
Collect all invoices from suppliers: greengrocer, butcher, beverage wholesaler and also small purchases at the supermarket. Every ingredient that goes on the plate must be included.
Note all ingredients with their price per kilo or per piece
Go through each invoice and write down: product name, packaging, price excl. VAT and converted to price per kilogram. This becomes your ingredient database.
Measure exactly how much you use per dish
Weigh all ingredients that go into one portion: meat, vegetables, sauce, oil, butter. Even the garnish counts. Be precise, because 10 grams difference costs you hundreds of euros per year.
Factor in trimming loss in your cost price
From a whole fish you only get 55% fillet. Divide your purchase price by the yield percentage to get the actual cost price. Otherwise you'll calculate too favorably.
Add up all ingredient costs per dish
Multiply the weight per ingredient by the price per kilo. Add everything up for the total cost price of the dish. Check that your food cost stays under 35%.
✨ Pro tip
Start by costing your three highest-volume dishes first, then calculate the exact grams of each ingredient using a digital scale for one full service. This gives you real-world portion data instead of guesswork.
Calculate this yourself?
In the KitchenNmbrs app you can do this in just a few clicks. 7 days free, no credit card.
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Frequently asked questions
Should I include VAT in my cost price calculation?
Never include VAT in cost calculations. You pay it on purchases but claim it back from tax authorities. Only the net amounts matter for true ingredient costs.
How often should I update my cost prices?
Monthly minimum, or immediately after spotting price increases on invoices. Suppliers adjust prices regularly, and delayed updates can kill your margins within weeks.
Should I also count small ingredients like salt and pepper?
Yes, but stay practical about it. Budget roughly €0.15 to €0.30 per portion for basic seasonings. For expensive spices like saffron or truffle oil, calculate precisely.
What if my supplier charges different prices per order?
Use the weighted average from your last three invoices, or stick with the most recent price. Suppliers run promotions, but calculate costs using standard pricing for consistency.
How do I calculate the cost price of composite sauces?
Create a separate recipe costing for each sauce. Add up all ingredients, divide by total yield, then calculate per-portion costs. A 30ml serving of hollandaise might cost €0.45 once you factor in egg yolks and butter.
Can I estimate cost prices instead of calculating exactly?
Most operators estimate and end up 4-9% higher in food costs than necessary. Over twelve months, that estimation error can cost you thousands in lost profit.
How do I handle ingredients used across multiple dishes?
Track each ingredient separately, then allocate portions to individual dishes. Olive oil might appear in six different recipes, but you need to know exactly how much each dish consumes.
📚 Sources consulted
- EU Verordening 852/2004 — Levensmiddelenhygiëne (2004) — Official source
- EU Verordening 853/2004 — Hygiënevoorschriften voor levensmiddelen van dierlijke oorsprong (2004) — Official source
- EU Verordening 1169/2011 — Voedselinformatie aan consumenten (2011) — Official source
- NVWA — Hygiënecode voor de horeca (2024) — Official source
- NVWA — Allergenen in voedsel (2024) — Official source
- Codex Alimentarius — International Food Standards (2024) — Official source
- FSA — Safer food, better business (HACCP) (2024) — Official source
- BVL — Lebensmittelhygiene (HACCP) (2024) — Official source
- Warenwetbesluit Bereiding en behandeling van levensmiddelen (2024) — Official source
- WHO — Foodborne diseases estimates (2024) — Official source
Food Standards Agency (FSA) — https://www.food.gov.uk
The HACCP standards shown in this application are for informational purposes only. KitchenNmbrs does not guarantee that displayed values are current or complete. Always consult the FSA or your local authority for the latest regulations.
Written by
Jeffrey Smit
Founder & CEO of KitchenNmbrs
Jeffrey Smit built KitchenNmbrs from 8 years of hands-on experience as kitchen manager at 1NUL8 Group in Rotterdam. His mission: give every restaurant owner control over food cost.
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