Most restaurant owners think bigger portions equal happier customers, but this myth kills profits daily. Choosing portions by gut feeling instead of math means you're likely losing money on every plate. The right portion size balances customer satisfaction with your target margins.
Why portion size is crucial for your profit
Your portion size directly determines your food cost percentage. Oversized portions mean inflated costs and shrinking profit. But portions that are too small? They'll disappoint guests and hurt your reputation.
💡 Example:
You serve salmon for €28.00 (incl. 9% VAT) and want 30% food cost:
- Selling price excl. VAT: €25.69
- Maximum ingredient costs: €25.69 × 0.30 = €7.71
- Salmon costs €32/kg after trim loss
- Maximum portion: €7.71 ÷ €32 = 241 grams salmon
The formula for ideal portion size
This calculation works backwards from what most people expect. Start with your desired margin, then calculate back to find the maximum portion size that maintains profitability.
Formula:
Maximum portion size = (Selling price excl. VAT × Desired food cost %) ÷ Price per kg main ingredient
⚠️ Note:
Always calculate with the price excl. VAT. Menu prices include 9% VAT for food, but your cost calculations need the base price.
Including side dishes and garnishes
Your main ingredient isn't the only cost on that plate. From years of working in professional kitchens, I've seen how these "small" costs add up fast:
- Vegetables and potatoes
- Sauces and butter
- Herbs and oil
- Plate decoration
💡 Example with side dishes:
Steak menu for €32.00 (excl. VAT €29.36), desired food cost 32%:
- Maximum total costs: €29.36 × 0.32 = €9.40
- Side dishes cost: €3.20
- Budget for steak: €9.40 - €3.20 = €6.20
- Steak €45/kg → maximum 138 grams meat
Different portion sizes at different times
You can vary portion sizes throughout the day, as long as your food cost percentages stay on target:
- Lunch: Smaller portions, lower price, same margin
- Dinner: Larger portions, higher price
- Happy hour: Adjusted portions for special prices
Testing and adjusting in practice
Start with your calculated portion size and watch how guests respond. Monitor how many plates come back clean and track any complaints about portion size.
💡 Practical test:
Serve your calculated portion for a week and count how many plates return completely empty. More than 90% empty? You could probably reduce portions by 10-15%. Less than 70% empty? Consider increasing the portion or adjusting the composition.
Digital help with portion management
Manually tracking portion sizes and costs eats up valuable time. Systems that automatically calculate your maximum portion size based on desired food cost percentages show you immediately if your dish will be profitable.
How do you calculate the ideal portion size? (step by step)
Determine your desired food cost percentage
Choose a food cost between 28-35% for most restaurants. For fine dining this can be higher, for fast food lower. This becomes your starting point for all calculations.
Calculate your maximum ingredient costs
Multiply your selling price (excl. VAT) by your desired food cost percentage. This is the maximum amount you can spend on all ingredients for this dish.
Subtract the costs of side dishes
Add up all costs for vegetables, sauces, garnishes and decoration. Subtract this from your maximum ingredient costs. The remaining amount is your budget for the main ingredient.
Calculate the maximum portion size
Divide your budget for the main ingredient by the price per kilogram. Note: use the actual price after trim loss, not the purchase price of the whole product.
Test and adjust in practice
Start with your calculated portion and monitor guest satisfaction and how much is left on plates. Adjust the portion size or composition if needed, within your budget.
✨ Pro tip
Test your 3 most expensive dishes first over the next 10 days. If those portion sizes hit your target margins, you've fixed the biggest profit leaks in your kitchen.
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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 calculate with the price including or excluding VAT?
Always excluding VAT. Menu prices include 9% VAT, but cost calculations need the base price. Otherwise your food cost appears artificially low.
How do I calculate trim loss with fish and meat?
Use the actual price after processing, not the purchase price. With 40% trim loss, €20/kg whole fish becomes €33.33/kg fillet. Calculate portions using that €33.33 price.
What if my calculated portion seems too small for guests?
You have three options: raise your selling price, accept a higher food cost, or replace expensive ingredients with cheaper alternatives. Never operate below your break-even point.
📚 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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