When ingredients become more expensive but you reduce portion sizes, your margin can still remain stable. It's about finding the right balance between cost per portion and customer acceptance. In this article you'll learn step by step how to calculate what the optimal portion size is when purchase prices have risen.
The formula for adjusted margin
When purchase prices rise and portions get smaller, use this calculation:
New cost per portion = (New purchase price per kg × New portion size in kg)
New food cost % = (New cost per portion / Selling price excl. VAT) × 100
💡 Example:
Your 250 gram steak used to cost €18/kg, now €22/kg (+22%). You're considering 220 gram portions:
- Old situation: €18/kg × 0.25 kg = €4.50 per portion
- New situation: €22/kg × 0.22 kg = €4.84 per portion
- Cost increases by only €0.34 instead of €1.00
At €32 selling price: food cost rises from 31.1% to 33.5%
What's acceptable to guests?
The art is reducing portions without guests noticing or objecting. Common adjustments:
- Meat/fish: 10-15% smaller usually goes unnoticed
- Side dishes: Up to 20% less is rarely noticed
- Sauces: Portion size can often be 25% smaller
- Garnish: Visually important, but weight less critical
⚠️ Heads up:
Never reduce by more than 20% at once. Regular guests will notice big differences. Do it gradually over 2-3 months.
Alternative strategies
Besides adjusting portion size, you have more options to protect your margin:
- Adjust recipes: Replace expensive ingredients with cheaper alternatives
- Switch suppliers: Compare prices and quality with other suppliers
- Raise menu prices: A €1-2 increase is less noticeable than smaller portions
- Seasonal menu: Switch to cheaper seasonal ingredients
💡 Example calculation:
Salmon rises from €24/kg to €28/kg. You're considering 160g instead of 180g portions:
- Old cost: €24 × 0.18 = €4.32
- New cost (same portion): €28 × 0.18 = €5.04
- New cost (smaller portion): €28 × 0.16 = €4.48
Result: only €0.16 cost increase instead of €0.72
Communication with your team
Brief your team on the new portion sizes. Use portioning tools like scales or measuring cups to ensure consistency. A chef who portions "by feel" might unintentionally keep serving the old larger portions.
Consider updating your recipes in a system like KitchenNmbrs, so everyone uses the same portion sizes and you automatically see the new food cost.
Monitor the results
Keep a close eye the first month after adjusting:
- Complaints about portion size
- Changes in average spending per guest
- Actual food cost versus calculated food cost
- Satisfaction scores or online reviews
If you hear complaints from more than 10% of guests, the portions have probably become too small.
How do you calculate the optimal portion size when prices rise?
Calculate your current cost per portion
Multiply the old purchase price per kilo by your current portion size in kilos. This is your reference point.
Determine your maximum cost increase
Decide how much euro cost increase per portion is acceptable for your margin. Usually you don't want more than 10-15% increase.
Calculate the new portion size
Divide your maximum cost per portion by the new purchase price per kilo. This gives you the maximum portion size in kilos.
Test customer acceptance
Try the new portion size for 1-2 weeks and monitor customer reactions. Adjust if needed before making the permanent switch.
✨ Pro tip
Check your food cost weekly the first month after portion adjustment. This way you'll immediately see if your team is consistently using the new measures and if your calculation works in practice.
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
How much smaller can a portion get without guests complaining?
Maximum 15-20% smaller at once. For meat and fish, 10-15% is safer. Do it gradually over several months if you want to reduce more.
Is it better to reduce portions or raise menu prices?
It depends on your target audience. With price-conscious guests, reducing portions works better. With quality-conscious guests, you can better raise the price and keep the portion.
How do I prevent my chef from using the old portion sizes?
Update your recipes in writing, use portioning tools like scales, and check regularly. A digital recipe system helps keep everyone on the same page.
Should I warn customers that portions are getting smaller?
No, unless the difference is very noticeable. You can communicate positively about 'refined portions' or 'adjusted recipes' if asked.
How do I calculate if reducing portions is more profitable than switching suppliers?
Compare the total cost per portion for both options. Calculate: (new supplier price × current portion) versus (old supplier price × smaller portion).
📚 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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