Which weight belongs in your recipe costing?
Use the weight of the ingredient in the condition your recipe needs. If you discard the packing liquid and serve drained solids, compare drained weight rather than the combined weight of solids and liquid. If your recipe uses both, cost the quantities actually used instead.
GOV.UK’s quantity-labelling guidance identifies drained net weight separately for solid foods packed in liquid or an ice glaze: https://www.gov.uk/food-labelling-and-packaging/food-labelling-what-you-must-show
Check the supplier specification and label, then measure usable output where your preparation method changes it. Record whether a weight means purchased, drained, trimmed or cooked food. Mixing those bases makes a price comparison unreliable.
What does the worked comparison assume?
Assume two interchangeable packs of the same ingredient meet your recipe’s quality requirements. Pack A costs £18.00, contains 3.00kg including packing liquid and provides 1.80kg drained solids. Pack B costs £22.00, also contains 3.00kg including liquid and provides 2.40kg drained solids.
Each dish uses 120g of drained solids. All other chosen direct costs total £2.40 per dish, including any packaging. Assume no additional preparation loss, no unsold portions and no difference in delivery charges or preparation costs. All usable food is eventually sold.
These are original illustrative inputs, not supplier quotations or measured product yields. Costs exclude recoverable purchase VAT and include non-recoverable VAT. The customer price is £12.00, including an explicitly assumed 20% sales VAT; that assumption does not classify any food item.
All worked numbers were checked using Python 3. Calculations retain full precision; money is displayed to pennies and margins to two decimal places.
How do you calculate cost per usable kilogram?
Cost per usable kilogram = pack cost ÷ usable kilograms.
Pack A: £18.00 ÷ 1.80kg = £10.00 per usable kilogram. Pack B: £22.00 ÷ 2.40kg = approximately £9.17 per usable kilogram.
Comparing the headline 3.00kg weights would give £6.00/kg for A and approximately £7.33/kg for B, apparently favouring A. That comparison includes liquid this recipe discards.
Convert the serving weight to kilograms: 120g = 0.120kg. Multiply the unrounded usable-kilogram cost by 0.120kg:
Pack A ingredient cost per dish = £1.20. Pack B ingredient cost per dish = £1.10.
Alternatively, A provides 15 servings and B provides 20 servings. Dividing each pack’s cost by those serving counts gives the same results. Keep any usable remainder in your stock calculation rather than automatically treating it as waste.
What happens to gross profit at the same menu price?
Add the other £2.40 of chosen direct costs. Total portion cost is £3.60 with A and £3.50 with B.
Net sale = gross customer price ÷ (1 + VAT percentage ÷ 100). Gross profit = net sale − portion cost. GP margin = gross profit ÷ net sale × 100.
At the assumed VAT rate, £12.00 ÷ 1.20 = £10.00 net sale.
Using A: £10.00 − £3.60 = £6.40 gross profit, giving 64.00% GP margin. Using B: £10.00 − £3.50 = £6.50 gross profit, giving 65.00% GP margin.
Across 100 identical sales, gross profit is £640.00 with A or £650.00 with B: a £10.00 difference. This holds prices, quantities and other costs constant; it predicts no change in customer demand. Neither margin is a recommended target. Gross profit still has to cover remaining business expenses and is not net or take-home profit.
Is drained yield the calculator’s wastage percentage?
No. Draining changes the amount of usable ingredient obtained from a purchase. The calculator’s wastage input means portions made but not sold.
First calculate recipe costs using usable ingredient quantities. If completed portions subsequently go unsold, apply that separate allowance once. Do not enter the discarded liquid percentage as unsold-portion wastage after already using drained weight in the recipe cost.
The calculator’s sold-portion formula is batch cost ÷ [portions made × (1 − unsold percentage ÷ 100)] + packaging per sold portion. This example assumes no unsold portions, so it needs no further adjustment. Calculation assumptions and rounding are explained at /methodology/.
How can you test a supplier change before ordering?
Open GP Calculator UK at / and choose Check my GP. Enter cost 3.60, customer menu price 12.00 and assumed VAT 20. Record GP pounds and margin, then change cost to 3.50. The input explanations at /#guide help you keep both calculations on the same cost basis.
Before choosing a pack, check whether you can use its contents within the applicable storage instructions. Compare delivery charges, minimum orders, preparation requirements and recipe performance. A lower usable-kilogram cost may be outweighed by additional costs or unsold stock.
Keep a short purchasing record containing the quote date, pack cost, usable weight, serving weight and resulting portion cost. Update the recipe when either the price or specification changes.
Which VAT assumptions must you replace?
Use the VAT treatment applicable to your actual sale. The 20% here demonstrates arithmetic only; the calculator does not classify food or decide whether you should charge VAT. HMRC explains catering and takeaway distinctions at https://www.gov.uk/guidance/catering-takeaway-food-and-vat-notice-7091 .
Use purchase costs excluding recoverable VAT and including VAT you cannot recover. Recovery has conditions and exceptions; registration alone does not settle every purchase. HMRC’s guidance is at https://www.gov.uk/charge-reclaim-record-vat/reclaim-vat-business-expenses .
This guide explains purchasing and menu-cost arithmetic, not personalised tax advice.
Sources
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Try your own figures
Use the free GP calculator to check selling prices, compare margins and save menu items on your device. Gross profit is before remaining business expenses.
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