Getting portion sizes wrong can destroy your profit margins before you even realize what's happening. Most restaurants eyeball their portions, but smart operators work backward from their target food cost percentage. This calculation method shows you exactly how much protein, starch, and garnish should land on each plate.
Why portion size matters so much
Your portion size controls how much money you make per dish. An extra 50 grams of meat per portion can flip a profitable dish into a loss leader. Many kitchens work by feel, but the math tells the real story.
⚠️ Watch out:
A steak of 250 grams instead of 200 grams costs you €1.00 extra per portion at €20/kg beef. At 100 portions per week: €5,200 per year.
The formula for ideal portion size
This calculation works backward from your target numbers. Start with your desired food cost percentage and work down to the exact gram weight you can afford.
Step 1: Calculate maximum ingredient costs
Maximum ingredient costs = Selling price (excl. VAT) × Desired food cost %
💡 Example:
Steak on menu: €32.00 incl. 9% VAT
- Selling price excl. VAT: €32.00 ÷ 1.09 = €29.36
- Desired food cost: 30%
- Max ingredient costs: €29.36 × 0.30 = €8.81
Step 2: Divide across main ingredient and side dishes
Your protein doesn't get the entire food cost budget. Reserve money for vegetables, sauce, and cooking oil too.
💡 Example breakdown of €8.81:
- Steak: €6.50
- Vegetables: €1.20
- Sauce: €0.80
- Oil/butter: €0.31
Remaining for steak: €6.50
Step 3: Calculate portion size
Portion size = Available budget ÷ Price per kg
💡 Example:
Beef costs €22/kg
- Budget for meat: €6.50
- Portion size: €6.50 ÷ €22 = 0.295 kg
- That's 295 grams of beef
Account for trim loss
Don't forget trim loss. You buy more raw product than what actually reaches the plate due to waste, fat trimming, and prep loss.
⚠️ Watch out:
At 15% trim loss you have 85% yield. Then your actual price becomes: €22 ÷ 0.85 = €25.88/kg for usable meat.
Different products, different approach
Each ingredient category needs its own portioning strategy. From tracking this across dozens of restaurants, I've seen how different ingredients behave:
- Meat/fish: Weigh exactly, account for trim loss
- Pasta/rice: Measure dry weight, account for expansion
- Vegetables: Account for peels and waste (10-25%)
- Sauces: Use standard spoons or portion scoops
Monitoring and adjustment
Your calculated portion size gives you a starting point. But you need to track actual costs to stay profitable.
- Measure your actual food cost per dish weekly
- Check if suppliers have raised prices
- Watch for seasonal effects on ingredient prices
- Train your kitchen team on consistent portions
How do you calculate the ideal portion size? (step by step)
Determine your maximum ingredient costs
Calculate your selling price excl. VAT and multiply by your desired food cost percentage. This gives you the total budget for all ingredients in the dish.
Divide costs across all ingredients
Subtract the costs of side dishes, sauces and garnishes from your total budget. The remaining amount is available for your main ingredient.
Calculate the portion size
Divide your available budget by the per-kilo price of your main ingredient. Don't forget to account for trim loss by dividing by the yield percentage.
✨ Pro tip
Weigh your actual portions for 10 consecutive service days using a digital scale. Most kitchens serve 15-25% larger portions than their recipes specify, which directly cuts into profit margins without anyone noticing.
Calculate this yourself?
In the KitchenNmbrs app you can do this in just a few clicks. 7 days free, no credit card.
Was this article helpful?
Frequently asked questions
Do I always need to account for trim loss in the calculation?
Yes, always factor in trim loss. Meat and fish typically have 15-25% waste from fat, bones, and trimming. Use your actual usable price per kg, not the raw purchase price, or your portions will blow your food cost.
What if my calculated portion seems too small for guests?
You have two choices: raise your menu price or accept a higher food cost percentage. Serving tiny portions damages your reputation, so make this decision consciously rather than hoping it works out.
How often should I recalculate my portion sizes?
Recalculate every 3 months minimum, or immediately when suppliers change prices. Ingredient costs shift constantly, especially proteins and seasonal produce.
Can I offer different portion sizes for the same dish?
Absolutely, but calculate separate selling prices for each size. A 300g steak can't have the same food cost percentage as a 200g portion. Price them proportionally.
How do I ensure my kitchen team makes consistent portions?
Use digital scales, standardized scoops, and spot-check weekly. Most kitchen teams gradually increase portion sizes over time without realizing it, which quietly destroys your margins.
Should I calculate portions differently for seasonal ingredients?
Yes, seasonal ingredients can swing 30-50% in price throughout the year. Adjust portions quarterly for seasonal items, or substitute different ingredients during expensive periods to maintain your food cost targets.
📚 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.
Standardize portions, stabilize margins
Varying portions mean varying costs. KitchenNmbrs records exact quantities per recipe so every plate costs the same. Try it free for 14 days.
Start free trial →