The relationship between portion size and inventory consumption determines how much you order and how much you have left over. Many head chefs estimate this, causing them to order too much or run short. In this article, you'll learn to precisely calculate how much inventory you need per portion.
Why connect portion size and inventory?
Your portion size directly determines how many ingredients you consume per day. If your chef serves 250 grams of steak instead of 200 grams, you consume 25% more meat than you think.
💡 Example:
You expect 50 steak portions of 200g:
- Calculated consumption: 50 × 200g = 10 kg
- Actual portion: 250g
- Actual consumption: 50 × 250g = 12.5 kg
Difference: 2.5 kg = 25% more than expected
The basic formula for inventory consumption
You calculate the relationship between portion and inventory like this:
Inventory consumption = Number of portions × Portion size per ingredient
This seems simple, but you need to account for:
- Trim loss (from whole product to portion)
- Cooking loss (what's lost during cooking)
- Variation in portion size by different cooks
- Reserve for busy moments
Step 1: Measure your actual portion size
Many business owners don't know what their chef actually serves. Measure this for a week:
💡 Practical example:
Weigh 10 random plates of the same dish:
- Plate 1: 220g main ingredient
- Plate 2: 240g main ingredient
- Plate 3: 210g main ingredient
- Average: 225g
You calculated 200g, but serve an average of 225g = 12.5% more
Step 2: Account for trim loss
From whole product to portion, something is always lost. You need to include this in your inventory calculation:
Required purchase = Net portion ÷ (100% - Trim loss%)
💡 Calculation example:
You want 50 portions of 200g salmon:
- Net needed: 50 × 200g = 10 kg fillet
- Trim loss whole salmon: 45%
- Gross purchase: 10 kg ÷ 0.55 = 18.2 kg whole salmon
So you need to order 18.2 kg to get 10 kg on the plate
⚠️ Note:
Divide by the yield, don't multiply by the loss. With 45% loss you divide by 0.55 (the yield).
Step 3: Plan for variation and busy times
Your inventory needs to be flexible. Plan 10-20% extra for:
- Unexpectedly busy evenings
- Larger portions by different cooks
- Damaged ingredients on delivery
- Tasting and testing in the kitchen
Calculate weekly inventory consumption
For your weekly order use this formula:
Weekly consumption = (Average portions/day × Portion size × 7 days) ÷ Yield × 1.15 (buffer)
💡 Complete example:
Pasta carbonara, average 25 portions per day:
- Bacon per portion: 40g
- Weekly consumption: 25 × 40g × 7 = 7 kg
- Bacon trim loss: 15%
- Gross purchase: 7 kg ÷ 0.85 = 8.2 kg
- With 15% buffer: 8.2 × 1.15 = 9.4 kg
Order 9.5 kg bacon for this week
Digital tracking vs. Excel
You can do these calculations manually, but it takes a lot of time. With an app like KitchenNmbrs:
- You set your portion size per dish
- You automatically calculate back to required inventory
- You see immediately what you need to order
- You track what you actually consume vs. what you order
This saves you hours of calculation per week and prevents you from ordering too much or too little.
How do you calculate inventory consumption per portion?
Measure your actual portion size
For a week, weigh the portions of your 5 best-selling dishes. Note the weight of each main ingredient per plate. Calculate the average per dish.
Calculate your trim loss percentage
Measure how much usable product you get from your raw purchase. For example: from 10 kg whole fish to 5.5 kg fillet = 45% trim loss. This varies by product and supplier.
Calculate back to required purchase
Use the formula: (Number of portions × Portion size) ÷ Yield × 1.15 buffer. This gives you the amount you need to order for the number of portions you want to make.
✨ Pro tip
Check your top 5 dishes weekly: weigh 3 random plates and compare with your standard portion size. Every 10 gram difference on a dish you sell 100 times per week costs you 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.
Was this article helpful?
Frequently asked questions
How much buffer should I include in my inventory calculation?
A buffer of 10-20% is standard. For fresh products that spoil quickly you keep less buffer (10%), for shelf-stable products you can take more buffer (20%). This depends on your delivery frequency and how predictable your sales are.
Do I need to account for trim loss if I order pre-portioned?
With pre-portioned purchases (like 200g steaks) you have no trim loss. However, there can still be cooking loss from shrinkage during cooking. Budget 5-10% for that.
What if my chef gives different portion sizes?
Measure for a week and take the average. Train your team on consistent portions using scales or portion spoons. Every gram difference costs money over a year.
How often should I check my portion size?
Check your 5 best-selling dishes monthly by weighing 10 random plates. If you have new cooks, do this weekly until portions are consistent.
Can I automate this calculation?
Yes, with a system like KitchenNmbrs you can record your recipes and portion sizes. The app then automatically calculates how much inventory you need per dish and for your overall planning.
📚 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.
Manage inventory without spreadsheets
Always know what you have in stock and what it's worth. KitchenNmbrs connects inventory to recipes and purchasing for complete oversight. Start your free trial.
Start free trial →