📝 Purchasing, suppliers & strategy · ⏱️ 3 min read

How do I calculate the purchase price per portion when...

📝 KitchenNmbrs · updated 07 Apr 2026

Quick answer
Here's what most kitchen managers get wrong: they compare lettuce prices without factoring in the hidden costs. Whole heads look cheaper on paper, but trimming loss and labor time tell a different story.

Here's what most kitchen managers get wrong: they compare lettuce prices without factoring in the hidden costs. Whole heads look cheaper on paper, but trimming loss and labor time tell a different story. You'll discover the real math behind both options.

The difference between heads and pre-cut

Lettuce purchasing comes down to two main choices: whole heads or pre-packaged lettuce. Each option carries distinct cost structures that require careful calculation.

? Example comparison:

For 100 portions of salad you need 5 kg of clean lettuce:

  • Whole heads: €1.20/head, 8 heads needed = €9.60
  • Pre-packaged lettuce: €3.20/kg, 5 kg needed = €16.00

But there's more to this story...

Calculate trimming loss for whole heads

Whole lettuce heads always generate trimming loss. You discard outer leaves, remove stems, and lose volume during washing and spinning.

? Trimming loss calculation:

Iceberg lettuce head of 800 grams:

  • Outer leaves: 150 grams waste
  • Stem: 80 grams waste
  • Washing and draining loss: 70 grams waste

Usable: 500 grams (62.5% yield)

The formula for actual price per kilo after trimming loss:

Actual price = Purchase price per head / (Usable weight in kg)

? Actual cost price:

Head at €1.20 with 500 grams usable:

€1.20 / 0.5 kg = €2.40 per kg clean lettuce

⚠️ Attention:

Most kitchens calculate using the purchase price per head but ignore trimming loss. This makes whole lettuce appear much cheaper than reality.

Include labor time in the calculation

Whole heads demand more labor than pre-packaged lettuce. Add this time as a legitimate cost item. One of the most common blind spots in kitchen management is underestimating the labor involved in basic prep work like lettuce processing.

  • Cleaning and cutting: 3-5 minutes per head
  • Washing and spinning: 2-3 minutes per head
  • Cleanup and waste disposal: 1-2 minutes per head

? Labor cost calculation:

8 heads for 100 portions, 6 minutes per head:

  • Total time: 48 minutes = 0.8 hours
  • Kitchen hourly rate: €18 (incl. employer taxes)
  • Labor costs: 0.8 × €18 = €14.40

Per 100 portions: €0.14 labor cost per portion

Total comparison per portion

Now you can compare the true costs per portion. Add up all cost items for an accurate comparison.

? Total overview 100 portions:

Whole heads:

  • 8 heads at €1.20 = €9.60
  • Labor costs = €14.40
  • Total = €24.00

Pre-packaged lettuce:

  • 5 kg at €3.20 = €16.00
  • Labor costs = €0 (ready to use)
  • Total = €16.00

Per portion: €0.24 vs €0.16 - pre-packaged saves €0.08 per portion

Scenarios where whole heads remain economical

Whole heads can still be more economical under certain conditions:

  • Large volumes: At 500+ portions daily, labor time per portion decreases significantly
  • Lower labor costs: If you handle prep personally or staff costs under €15/hour
  • Reduced trimming loss: Fresh, smaller heads can achieve 75% yield
  • Quality premium: If customers notice the difference and pay more for fresh lettuce

⚠️ Attention:

Always calculate using your own numbers. Trimming loss and labor costs vary by kitchen. Track for one week to determine your actual yield.

Account for seasonal price swings

Lettuce prices swing dramatically by season. Whole heads might cost €0.80 in summer and €2.00 in winter. Pre-packaged lettuce shows fewer price fluctuations.

So recalculate monthly to determine which option saves money. A food cost calculator helps track these calculations and automatically updates your cost price when supplier prices change.

How do you calculate the actual purchase price per portion?

1

Measure the trimming loss of whole heads

Weigh 10 heads before and after cleaning. Calculate the average yield percentage. This becomes your standard for all calculations.

2

Calculate the actual price per kilo

Divide the price per head by the usable weight in kilograms. For pre-packaged lettuce use the supplier's price per kilo directly.

3

Add labor costs

Measure how much time you spend cleaning per head. Multiply by your hourly rate (including employer taxes) and add to the ingredient costs.

4

Compare total costs per portion

Divide the total costs by the number of portions you make with it. Choose the option that is cheapest per portion for your situation.

✨ Pro tip

Track your lettuce prep for exactly 14 days: weigh every head before and after trimming, time every step. Most kitchens discover their actual yield is 8-12% lower than estimated, completely changing the cost equation.

Calculate this yourself?

In the KitchenNmbrs app you can do this in just a few clicks. 7 days free, no credit card.

Try KitchenNmbrs free →

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Frequently asked questions

How much trimming loss should I account for with iceberg lettuce?
Plan for 35-40% trimming loss with iceberg lettuce. That translates to 60-65% yield. Track this yourself for one week to establish your specific percentage.
Should I include labor costs in cost price calculation?
Absolutely, labor costs are real expenses. If you spend 10 minutes cutting lettuce at €18/hour, that's €3.00 in labor you must account for.
What's the break-even point for choosing whole heads over pre-cut?
Whole heads typically become economical at 300+ portions daily, assuming €18/hour labor costs. Below that volume, pre-cut usually wins. But your specific trimming loss percentage and labor rate will shift this number.
How often should I recalculate this comparison?
Monthly minimum, since lettuce prices fluctuate dramatically by season. Winter whole heads can cost 2-3x more than summer prices.
Can I apply this method to other vegetables?
Yes, this calculation works for any vegetable with trimming loss: peppers, onions, carrots, etc. Always measure your specific yield percentage for each item.
What if my supplier offers volume discounts on whole heads?
Factor volume discounts into your per-head cost before calculating. A 15% discount on 50+ heads can tip the scales back toward whole heads, especially during peak season.
ℹ️ This article was prepared based on official sources and professional expertise. While we strive for current and accurate information, the content may differ from the most recent regulations. Always consult the official authorities for binding standards.

Sources consulted

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.

JS

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.

8 years kitchen manager at 1NUL8 Group Rotterdam
Expertise: food cost management HACCP kitchen management restaurant operations food safety compliance

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