GP Calculator UK / About & methods
About GP Calculator UK and its calculation methods
GP Calculator UK is a free browser-based tool operated by Fran Harvey for cafés, kitchens, caterers and other food businesses. It helps compare prices and costs using the figures you enter. It is an independent tool, not affiliated with Brakes or HMRC.
What does the calculator measure?
Gross profit is net sales minus the cost scope entered by the user. It is not net profit or take-home pay. Any wages, rent, utilities or other expenses not included in your entered cost remain to be paid. The calculator does not forecast demand or recommend a universal target margin.
Definitions and formulas
Let C be entered portion cost, S customer selling price, V sales VAT percentage and G target GP percentage. Percentages are entered as numbers such as 20 and 70.
- Net sale N
- S ÷ (1 + V ÷ 100)
- VAT amount
- S − N
- Gross profit P
- N − C
- GP margin (%)
- P ÷ N × 100, for N greater than zero
- Markup (%)
- P ÷ C × 100, for C greater than zero; undefined at zero cost
- Target customer price
- C ÷ (1 − G ÷ 100) × (1 + V ÷ 100), with G below 100%
- Maximum portion cost
- N × (1 − G ÷ 100)
A worked calculation you can reproduce
Enter cost £3.75, customer price £15 and assumed VAT 20% in Check my GP. Net sales are £12.50, VAT £2.50, gross profit £8.75, margin 70% and markup 233.33% before display rounding. At the same price, a cost of £4.25 gives £8.25 GP and a 66% margin.
How are packaging and waste treated?
Cost per sellable portion = batch ingredient cost ÷ [portions made × (1 − unsold portion percentage ÷ 100)] + packaging per sold portion. A £40 batch of 10 portions with 20% unsold leaves 8 sellable portions: £5 each before packaging. With £0.30 packaging each the cost is £5.30. This models unsold portions, not cooking yield loss. Do not count the same loss twice.
VAT and consistent cost inputs
Enter the VAT rate applicable to the specific sale. The tool does not classify food, determine registration obligations or decide what VAT can be recovered. Exclude recoverable purchase VAT from costs and include VAT you cannot recover. The 20% used in examples is an arithmetic assumption. Consult HMRC catering and takeaway guidance and HMRC purchase VAT guidance for tax treatment.
Rounding and comparisons
The target calculation can produce fractions of a penny. Customer prices are displayed to two decimal places; comparison cards and saved items use actual penny prices. A rounded price may give a slightly different margin from the target. A per-100-sales comparison holds volume constant and does not predict customer response.
Sources, authorship and corrections
Guides use AI-assisted research and drafting, with sources linked on each page and worked arithmetic checked before publication. That process does not establish professional accounting or tax review. Publication dates identify when a guide was released; a later date is used when its content is revised. If you spot an error, retain the page URL, figures and VAT assumptions so the calculation can be reproduced. Check the official source and your adviser before relying on tax treatment.
Using and saving your figures
Calculations run in the browser; saved menu items stay in that browser and do not sync across devices. Export a backup before clearing browser data. See the privacy notice for hosting, advertising and consent information.