Ingredient prices shift weekly, sometimes daily. Your supplier adjusts pricing monthly, leaving you guessing about actual costs until invoices arrive. Here's how to nail down accurate purchase prices per portion despite constant fluctuations.
Why price swings destroy your margins
Too many restaurant owners stick with last month's pricing data. When suppliers bump up costs and you're still calculating with outdated numbers, profits disappear silently.
⚠️ Watch out:
A 10% price increase on your main ingredients can raise your food cost from 30% to 33%. Over a year, that costs you thousands of euros in profit.
The accurate calculation method
For ingredients with shifting prices, you'll need a weighted average of actual purchases:
Average purchase price = (Total purchase value period) / (Total quantity purchased period)
💡 Example:
You buy salmon 3 times this month:
- Week 1: 5 kg for €18/kg = €90
- Week 2: 3 kg for €20/kg = €60
- Week 3: 4 kg for €22/kg = €88
Total: 12 kg for €238
Average price: €238 / 12 kg = €19.83/kg
Monthly price updates
Block out 45 minutes on month's first business day for price revisions. Target your 12-15 core ingredients — they drive 80% of food costs anyway.
- Pull invoices from the previous month
- Calculate weighted averages per ingredient
- Update recipe costs with fresh numbers
- Verify menu pricing still works
This pattern we see repeatedly in restaurant financials: operators who skip monthly updates lose 2-4% in margins annually.
Forward-looking price planning
Request next month's price estimates from suppliers. You can then decide whether menu adjustments or dish promotions make sense before costs hit.
💡 Example:
Your steak currently has 32% food cost. If beef becomes 15% more expensive:
- New food cost becomes: 32% × 1.15 = 37%
- Too high to sell profitably
- Action: raise menu price or temporarily promote fish
Digital tracking systems
Software solutions can automatically calculate price changes across your menu. Input fresh purchase prices and instantly spot dishes that've become unprofitable.
How do you calculate the correct purchase price per portion?
Gather all invoices from last month
Collect all supplier invoices together. Note per main ingredient: how much kg you bought and what you paid. Add up different deliveries of the same product.
Calculate the weighted average per ingredient
Divide the total purchase value by the total quantity. For example: €238 worth of salmon for 12 kg = €19.83 per kg. This is your actual average purchase price from last month.
Calculate through to portion price and check food cost
Multiply the new kilogram price by the weight per portion. Check if your food cost stays under 35%. If not, you need to raise your menu price or adjust the dish.
✨ Pro tip
Track your top 8 ingredients representing 75% of purchase volume every 3 weeks instead of monthly. These high-impact items deserve closer monitoring since small changes create big margin swings.
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
Do I need to update my prices every week?
Monthly works for most ingredients. Only highly volatile items like fresh fish or seasonal produce might need weekly tracking.
What if I buy the same product from multiple suppliers?
Combine all purchases for the weighted average. Example: 3 kg at €18 + 2 kg at €20 = 5 kg for €94 = €18.80 average.
How do I prevent price increases from eating into my profit?
Monitor food costs monthly on top sellers. If they creep above 35%, either raise menu prices or source cheaper alternatives.
Can't I just use the latest purchase price?
That skews your numbers badly. Your inventory mixes purchases at different price points, so weighted averages show true costs.
📚 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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