Trim loss on potatoes determines how much you actually pay per kilo of usable product. Many kitchens calculate based on purchase price, but forget that you lose weight when peeling and removing eyes and bad spots. Here's how to calculate exactly what your potatoes really cost.
What is trim loss on potatoes?
Trim loss is the weight difference between what you buy and what you can actually use. With potatoes, this includes peels, eyes, green spots, and bad pieces that you throw away.
💡 Example:
You buy 10 kg of potatoes for €12.50 (€1.25/kg)
- After peeling: 8.2 kg usable
- Trim loss: 1.8 kg (18%)
- Actual price: €12.50 / 8.2 kg = €1.52/kg
You're paying 22% more than you thought!
The formula for trim loss
Calculate trim loss in two steps:
Step 1 - Trim loss percentage:
Trim loss % = ((Purchase weight - Usable weight) / Purchase weight) × 100
Step 2 - Actual price per kilo:
Actual price = Purchase price per kg / (Yield % / 100)
Where: Yield % = 100% - Trim loss %
⚠️ Important:
Always divide by the yield, don't multiply by the trim loss! You have less product, so it becomes more expensive per kilo.
Trim loss by potato type
Trim loss varies by potato type and how you process them:
- Waxy potatoes: 15-20% (thin skin)
- Starchy potatoes: 18-25% (thicker skin)
- New potatoes: 8-12% (very thin skin)
- Old potatoes (many eyes): 25-30%
💡 Example calculation:
Starchy potatoes for mash:
- Purchase: 5 kg for €6.25 (€1.25/kg)
- After peeling: 4 kg usable
- Trim loss: 20%
- Yield: 80%
Actual price: €1.25 / 0.80 = €1.56/kg
Impact on your food cost
This difference has a major impact on your food cost calculation. If you calculate with €1.25/kg but actually pay €1.56/kg, you're off by 25%.
💡 Impact example:
Potato gratin with 200g potatoes per portion:
- Expected: 0.2 kg × €1.25 = €0.25 per portion
- Actual: 0.2 kg × €1.56 = €0.31 per portion
- Difference: €0.06 per portion
At 100 portions per week: €312 per year in extra costs!
Minimizing trim loss
You can reduce trim loss with the right approach:
- Buy quality: Better potatoes have fewer eyes and defects
- Peel thinner: Train your team to peel efficiently
- Use peelers: Faster and less waste than regular knives
- Check on delivery: Reject batches with many green spots
Track it digitally
Manually tracking trim loss takes time. With a system like KitchenNmbrs you can set the average trim loss per ingredient, so your food cost is calculated automatically and correctly.
How do you calculate potato trim loss? (step by step)
Weigh before and after processing
Weigh a representative amount of potatoes (at least 2-3 kg) before peeling. Peel them the way you normally do and weigh the usable weight afterward. Record both weights accurately.
Calculate the trim loss percentage
Subtract the usable weight from the purchase weight. Divide this by the purchase weight and multiply by 100. For example: (3kg - 2.4kg) / 3kg × 100 = 20% trim loss.
Calculate the actual price per kilo
Divide your purchase price per kilo by the yield (100% minus trim loss%). With 20% trim loss and €1.25/kg purchase: €1.25 / 0.80 = €1.56/kg actual price. Use this figure in your food cost calculations.
✨ Pro tip
Measure your trim loss on a quiet day with different team members. That way you get a realistic average and see if everyone peels equally efficiently.
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 trim loss is normal for potatoes?
For regular potatoes, 15-25% trim loss is normal, depending on quality and type. New potatoes have less loss (8-12%), old potatoes with many eyes have more (up to 30%).
Should I include trim loss in my menu price?
Absolutely. If you calculate with the purchase price but have 20% trim loss, you're underestimating your costs by 25%. This can make the difference between profit and loss on a dish.
Can I reduce potato trim loss?
Yes, by buying quality, peeling thinner, and training your team. Good storage also helps - potatoes that sprout or turn green produce more waste.
How often should I remeasure trim loss?
Measure it with each new supplier and when seasons change. Potatoes from different harvests can have different losses. Checking once per quarter is smart.
Does trim loss differ by cooking method?
Yes. For fries you peel thinner than for mash, so less loss. Potatoes cooked in their skin (baked) have no trim loss at all, just a wash.
📚 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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