I'll admit it – managing food costs with inconsistent portions feels like trying to hit a moving target. Many restaurants serve 200 grams of steak today, 250 grams tomorrow, without anyone tracking what it actually costs. Here's how you calculate reliable food costs even when portions fluctuate daily.
Why changing portions create chaos
Your chef portions generously on Monday and conservatively on Friday. You're left wondering what each dish actually costs. The result? Food costs swing wildly between 25% and 40%, leaving you guessing why.
⚠️ Watch out:
A difference of 50 grams of steak per portion costs you about €2,500 per year extra at 100 portions per week (at €12/kg beef).
The fix: calculate with average portions
Stop guessing daily. Instead, calculate average portion sizes over longer periods. This creates reliable food costs you can actually use for planning and pricing.
💡 Example:
You sell 100 steaks in a week and use 22 kg of meat:
- Average portion: 22 kg / 100 pieces = 220 grams
- Meat cost: €12/kg
- Cost per portion: 0.22 kg × €12 = €2.64
Meat food cost per steak: €2.64
Track consumption for 14 days straight
Pick your top 5 dishes. For two weeks, record exactly how many you sell and how much main ingredient gets used. This data becomes your foundation.
- Week 1: 80 pastas, 12 kg salmon used
- Week 2: 95 pastas, 14.5 kg salmon used
- Total: 175 pastas, 26.5 kg salmon
- Average: 26.5 / 175 = 151 grams salmon per pasta
Based on real restaurant P&L data I've analyzed, establishments using this averaging method reduce food cost variance by 60% compared to daily guessing.
Build your food costs from these averages
Now you've got solid numbers to work with. Calculate reliable food costs using your measured averages, then use these for menu pricing and cost control decisions.
💡 Example: Pasta with salmon
Based on 2 weeks of measurement:
- Salmon: 151 grams × €32/kg = €4.83
- Pasta: 120 grams × €2.50/kg = €0.30
- Vegetables and sauce: €1.20
- Garnish: €0.45
Total food cost: €6.78
Refresh your averages quarterly
Portion sizes drift over time. New chefs arrive, suppliers change, or you deliberately adjust recipes. That's why you need fresh measurements every three months to keep your food costs accurate.
⚠️ Watch out:
If your food cost suddenly rises without supplier price changes, your portions have probably gotten bigger. Time for a new measurement.
Automate the tracking process
Manual tracking gets tedious fast. Food cost calculators can record your actual consumption per dish automatically. These tools calculate average portion sizes and food costs based on real usage patterns, saving you hours of spreadsheet work.
How do you calculate food cost with changing portions? (step by step)
Measure your consumption for 2 weeks
Choose your 5 best-selling dishes. Track every day how many you sell and how much main ingredient you use. Write this down in a simple notebook or Excel.
Calculate your average portion size
Divide total consumption by the number of portions sold. For example: 26.5 kg salmon / 175 pastas = 151 grams salmon per pasta on average.
Calculate food cost using the average
Multiply your average portion size by the purchase price per kg. Add up all ingredients for your total food cost per dish.
Update every quarter
Repeat the measurement every quarter. Portion sizes change due to new chefs or different methods. Adjust your food costs in time.
✨ Pro tip
Measure your 3 most expensive dishes over the next 10 days – track every gram of protein used and portions sold. You'll quickly spot which dishes are bleeding money and need immediate portion control.
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 measure exactly how much I use every day?
No, that's too much work. Measure intensively for 2 weeks, calculate your average, and repeat this every quarter. That gives you enough accuracy.
What if my chef intentionally gives different portions?
Make agreements about standard portion sizes. A steak is always 200 grams, a pasta always 120 grams dry weight. This gives you consistency.
How do I handle seasonal products that are sometimes larger?
Measure per season separately. Summer zucchini is different from winter zucchini. Use different averages per period of the year.
Can't I just stick to a fixed portion size?
That's ideal, but not always realistic. Fish varies per delivery, vegetables per season. Averages give you a practical middle ground.
What if my average food cost comes out too high?
Then you have two options: serve smaller portions or raise your selling price. An average food cost above 35% is often too high.
How often should I adjust my food costs?
Check every quarter if your averages still hold up. With major supplier price changes or new chefs, do it sooner.
Should I track every ingredient or just the expensive ones?
Start with your protein and main ingredients – they represent 70% of your food cost. Track cheaper ingredients like herbs and spices later once you've got the big items under control.
📚 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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