Working with liters in cost price calculation is common for sauces, soups and drinks. The tricky part: you buy per liter, but serve per portion. Converting...
Most restaurants struggle with liquid cost calculations because they purchase by the liter but serve by the portion. Converting from bulk liquid purchases to individual serving costs requires precise math. The difference between accurate and estimated calculations can impact your profit margins by 15-20%.
Converting liters to portions: the foundation
You'll purchase most liquids by the liter, yet serve them in 100ml, 250ml, or 300ml portions. Calculate your cost per portion by dividing the liter price by how many portions that liter produces.
💡 Example:
Tomato juice costs €2.40 per liter, and you're serving 200ml portions.
- 1 liter = 1000ml
- 1000ml ÷ 200ml = 5 portions per liter
- Cost price per portion: €2.40 ÷ 5 = €0.48
The essential formula for portion costs
Every liquid follows this calculation:
Cost price per portion = Price per liter ÷ (1000ml ÷ ml per portion)
Or the simplified version:
Cost price per portion = (Price per liter × ml per portion) ÷ 1000
💡 Soup calculation:
Your tomato soup runs €3.20 per liter. Each bowl contains 300ml.
- Cost price: (€3.20 × 300ml) ÷ 1000 = €0.96
- Alternative method: €3.20 ÷ 3.33 portions = €0.96
Accounting for evaporation and waste
Hot liquids like soups and sauces always lose volume during preparation. Build in 5-10% loss for accurate cost calculations. This represents one of the most common blind spots in kitchen management - ignoring evaporation can underestimate your true costs significantly.
⚠️ Note:
Hot soups and sauces lose 5-10% through evaporation. That liter of soup yields 900-950ml, not the full 1000ml. Your cost calculations must reflect this reality.
💡 Loss calculation example:
Vegetable soup costs €4.00 per liter. After cooking, you've got 950ml remaining. Portion size: 250ml.
- Actual portions: 950ml ÷ 250ml = 3.8 portions
- Real cost per portion: €4.00 ÷ 3.8 = €1.05
Without factoring loss, you'd miscalculate at €1.00.
Working with sauces and dressings
Sauces and dressings require milliliter precision since portion sizes are small. Even tiny miscalculations add up across hundreds of plates.
- Salad dressing: 15-20ml per portion
- Hot sauce: 30-50ml per portion
- Jus: 20-30ml per portion
- Soup: 250-300ml per portion
💡 Dressing calculation:
Balsamic dressing runs €8.50 per liter. You're using 20ml per salad.
- Cost price: (€8.50 × 20ml) ÷ 1000 = €0.17 per salad
- 1 liter serves 50 salads
Beverage cost calculations
Drinks are straightforward since there's no cooking loss. Calculate directly from liter price to portion cost.
- Juices: 200-250ml
- Soft drinks: 250-300ml
- Water: 250ml (standard glass)
- Wine per glass: 125ml or 150ml
Essential measurement tips
Measure portion sizes with actual measuring cups rather than estimating. A 50ml difference per portion dramatically impacts your cost calculations.
Track evaporation rates for each hot preparation regularly. These percentages vary based on your specific recipes and cooking methods.
How do you calculate cost price per portion? (step by step)
Determine your portion size
Measure exactly how many milliliters you serve per portion. Use a measuring cup, not an estimate. For soup 250-300ml is normal, for sauces 30-50ml.
Calculate number of portions per liter
Divide 1000ml by your portion size. At 250ml portion: 1000 ÷ 250 = 4 portions per liter. Account for 5-10% loss with hot preparations.
Divide liter price by number of portions
Cost price per portion = liter price ÷ number of portions. At €3.20 per liter and 4 portions: €3.20 ÷ 4 = €0.80 per portion. Check this regularly when prices change.
✨ Pro tip
Test your evaporation rate once per recipe by measuring exactly what goes into the pot versus what comes out after cooking. Document this percentage - a 1-liter batch that yields 920ml has an 8% loss rate you can apply to all future cost calculations.
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Frequently asked questions
Do I always need to account for evaporation in my calculation?
Hot preparations lose 5-10% volume through evaporation - soups, sauces, and jus all require loss calculations. Cold drinks and dressings don't have evaporation issues.
How do I know how many milliliters I serve per portion?
Use a measuring cup to check actual portions. Have your chef ladle a normal serving, then measure it precisely. Most kitchens underestimate their actual portion sizes.
Can I use this method for wine per glass too?
Absolutely - wine follows the same formula. Standard wine portions are 125ml or 150ml, so a 750ml bottle yields 5 or 6 glasses respectively.
What if I use different portion sizes?
Calculate each portion size separately. Small, large, and extra-large portions each need their own individual cost calculations.
How often should I recalculate my cost prices?
Review supplier prices monthly and recalculate immediately if prices change more than 10%. This prevents your menu prices from falling behind cost increases.
Should I factor in spillage and kitchen waste beyond evaporation?
Yes, add 2-3% for spillage and waste on top of evaporation losses. This accounts for prep accidents, over-portioning, and end-of-batch waste that can't be served.
📚 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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