You buy tomatoes per kilo but sell them per piece in your dishes. How do you calculate the right cost price? Many hospitality entrepreneurs guess, which causes them to lose money without knowing it. In this article, you'll learn step-by-step how to convert from kilo price to per-piece price.
Why this matters so much
If you buy a tomato for €3.50 per kilo, that doesn't mean each tomato costs €3.50. The weight varies per piece. And if you don't calculate this correctly, your food cost won't add up.
⚠️ Watch out:
Many entrepreneurs calculate with an estimated average. "A tomato is about €0.50." That can add up to €100+ per month if you use a lot.
The basic formula
For every ingredient you buy by weight but use per piece, this applies:
Cost price per piece = (Purchase price per kg ÷ 1000) × Average weight per piece in grams
💡 Example:
Tomatoes cost €3.50 per kilo. Average weight: 180 grams per piece.
- €3.50 ÷ 1000 = €0.0035 per gram
- €0.0035 × 180 grams = €0.63 per tomato
Cost price: €0.63 per tomato
How do you determine the average weight?
Weigh 10 pieces of the same product and divide by 10. Do this with every delivery, because weights vary by season and supplier.
- Summer tomatoes: often heavier (200-220 grams)
- Winter tomatoes: lighter (150-180 grams)
- Organic products: more variation in weight
- Different suppliers: different sizes
💡 Example onions:
Onions €1.80/kg, average 120 grams per piece:
- €1.80 ÷ 1000 = €0.0018 per gram
- €0.0018 × 120 = €0.216 per onion
Rounded: €0.22 per onion
Practical tips for different products
Each product requires a different approach:
- Lemons: Weigh without skin if you only use the juice
- Potatoes: Weigh after peeling for the net cost price
- Bell peppers: Weigh after removing the seed core
- Meat per piece: Calculate with the weight that goes on the plate
⚠️ Watch out:
Don't forget cutting waste. If you throw away 20% (peels, seeds), add that to your cost price. An onion at €0.22 becomes €0.27 if you throw away 20%.
Keep track of seasonal variation
Prices and weights change by season. Update your calculations at least monthly, or whenever your supplier has a major price change.
💡 Real-world restaurant example:
Restaurant uses 200 tomatoes per week:
- Estimated: €0.50 per piece = €100/week
- Actual: €0.63 per piece = €126/week
- Difference: €26/week = €1,352/year
Impact: €1,352 per year underestimated
Digital help with calculations
Manual calculations take time and errors creep in. An app like KitchenNmbrs automatically converts from kilo price to per-piece price, tracks seasonal variations, and alerts you to major price changes.
How do you calculate cost price per piece? (step by step)
Weigh 10 pieces and calculate the average
Take 10 pieces of the same product from your delivery. Weigh them separately and calculate the average weight. This gives you the most accurate picture.
Calculate cost price per gram
Divide your purchase price per kilo by 1000. If tomatoes cost €3.50/kg, that's €0.0035 per gram. You need this base for the final calculation.
Multiply by average weight
Multiply the cost price per gram by the average weight per piece. €0.0035 × 180 grams = €0.63 per tomato. Check this again every month.
✨ Pro tip
Check your 5 most used ingredients that you use per piece. If those cost prices are correct, you've solved 80% of your problem and save hundreds of euros per year.
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
Do I have to do this for every product again?
Yes, each product has a different weight and different price fluctuations. Do it at least for your 10 most used ingredients that you use per piece.
How often should I recalculate the average weight?
With every new supplier and at least every 2 months. Seasons significantly affect the weight of vegetables and fruit.
What if the weight varies greatly per piece?
Then sort by size. Calculate separate cost prices for small, medium, and large pieces. Use the size you serve most often.
Should I include cutting waste in this calculation?
Yes, if you throw away parts, add those. An onion at €0.22 becomes €0.27 if you throw away 20% due to peels and bad parts.
Can't I just use a fixed price per piece?
You can, but then you risk errors. Weights and prices change by season. A fixed price is only accurate for a few months.
⚠️ 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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