Are you calculating fish costs correctly, or are you losing money on every fillet? Trimming loss often reaches 50%, meaning your actual price per kilo doubles from what you paid for whole fish. Most kitchens calculate based on purchase price while they're actually paying premium fillet rates.
Why calculate trimming loss with fish?
If you buy whole fish for €18 per kilo, you might think your fillet costs €18 per kilo. But after removing the head, bones, skin and fins, you often only have 50-60% left. Your actual fillet price then becomes €30-36 per kilo.
⚠️ Watch out:
Many business owners still calculate based on the purchase price of whole fish in their food cost calculation. This makes your food cost appear lower than it actually is.
The trimming loss formula for fish
Calculating net portion weight happens in two steps:
- Step 1: Calculate the yield percentage
- Step 2: Calculate the net weight per portion
Yield formula:
Yield % = (Net weight after processing / Gross purchase weight) × 100
Net portion weight formula:
Net portion weight = Desired fillet weight / (Yield % / 100)
💡 Example:
You want to serve 200 grams of salmon fillet per portion.
- Whole salmon purchase weight: 2.0 kg
- After filleting: 1.1 kg fillet
- Yield: (1.1 / 2.0) × 100 = 55%
Net portion weight: 200g / 0.55 = 364 grams whole salmon per portion
Typical trimming loss per fish type
Each type of fish has a different trimming loss percentage. Here are common figures:
- Salmon (whole): 40-50% trimming loss (50-60% yield)
- Sea bass: 45-55% trimming loss (45-55% yield)
- Dorade: 40-50% trimming loss (50-60% yield)
- Tuna (whole): 35-45% trimming loss (55-65% yield)
- Cod: 30-40% trimming loss (60-70% yield)
⚠️ Watch out:
These percentages are guidelines. Actual trimming loss depends on the size of the fish, your filleting technique and how precisely you work.
Impact on your food cost
Trimming loss has a direct impact on your food cost. If you don't account for this, your food cost calculation won't be correct.
After managing kitchen operations for nearly a decade, I've seen restaurants lose thousands annually by miscalculating fish costs. The difference between theoretical and actual portions can destroy your margins.
💡 Example food cost impact:
Salmon fillet 200 grams per portion:
- Whole salmon: €18/kg
- Yield: 55%
- Actual fillet price: €18 / 0.55 = €32.73/kg
- Cost per portion: 0.2 kg × €32.73 = €6.55
Difference: €6.55 instead of €3.60 (if you calculate based on purchase price)
How do you measure trimming loss in practice?
The most accurate way is to measure it yourself with a few fish:
- Weigh the whole fish before processing
- Fillet the fish the way you normally do
- Weigh the net fillet weight
- Calculate the yield percentage
- Repeat this with 3-5 fish for an average
Tools like KitchenNmbrs allow you to save this yield percentage per fish type, so your food costs calculate correctly automatically.
How do you calculate net portion weight after trimming loss? (step by step)
Measure the yield of your fish
Weigh a whole fish before processing and weigh the net fillet weight after filleting. Calculate the yield: (net weight / gross weight) × 100. Do this with 3-5 fish for a reliable average.
Calculate the required purchase weight
Divide your desired portion weight by the yield percentage. For example: 200 grams fillet at 55% yield = 200 / 0.55 = 364 grams whole fish per portion.
Calculate the actual food cost
Multiply the required purchase weight by your purchase price per kilo. At 364 grams and €18/kg = 0.364 × €18 = €6.55 per portion. This is your actual ingredient cost for the fish.
✨ Pro tip
Test your trimming loss calculations during your slowest service day each month. Weigh 3 whole fish before processing, then measure your final usable portions - this 15-minute exercise can save hundreds in miscalculated food costs.
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
Can't I just estimate how much trimming loss I have?
Estimating often leads to errors of 10-15%. With 100 fish dishes per week, this can add up to hundreds of euros per month. Measuring once gives you the correct figures for months.
Does trimming loss differ per supplier?
Yes, definitely. Larger fish have relatively less trimming loss than smaller ones. The quality of the fish and how cleanly it's been prepared also affects the yield.
Do I need to measure separately for each fish type?
Yes, each fish type has different trimming loss. Salmon has more fat and skin than, for example, cod. Measure at least your 3 most commonly used fish types separately.
How often do I need to measure trimming loss again?
With a new supplier or if you notice you're getting more or less fillet than expected. Otherwise, checking 1-2 times per year is sufficient.
Does the skin count toward trimming loss?
That depends on how you serve it. If you serve fillet with skin, you count the skin in your net weight. If you serve without skin, then skin is trimming loss.
Should I factor in bones removed during filleting for yield calculations?
Absolutely - backbone, rib bones, and pin bones all count as waste. Some fish like salmon have more bone density than others. Your yield percentage must reflect the actual edible portion you're serving guests.
What if my fish arrives pre-portioned from the supplier?
You still need to account for any additional trimming you do in-house. Pre-portioned doesn't always mean kitchen-ready - you might still remove skin, bloodlines, or adjust portion sizes.
⚠️ EU Regulation 1169/2011 — Allergen Information — https://eur-lex.europa.eu/eli/reg/2011/1169/oj
The allergen information on this page is based on EU Regulation 1169/2011. Recipes and ingredients may vary by supplier. Always verify current allergen information with your supplier and communicate this correctly to your guests. KitchenNmbrs is not liable for allergic reactions.
In the UK, the FSA enforces allergen regulations under the Food Information Regulations 2014.
📚 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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