A profit calculator is only useful if the inputs reflect the real economics of the product. Leaving out a small fee can make a weak SKU look healthy, while mixing VAT-inclusive and VAT-exclusive figures can distort the result even more.
Start with the selling price
Decide whether your calculation is based on gross customer price or net revenue. For VAT-registered UK businesses, make sure VAT treatment is handled consistently across the model.
Include landed product cost
Landed cost can include the supplier price, packaging, freight, duty, inspection and other costs required to get one sellable unit into the fulfilment network. Do not rely only on the factory unit price if the other costs are material.
Marketplace fees
Common per-order costs include the referral fee and fulfilment fee. Storage, removal, aged-inventory charges and programme-specific fees may also matter, but not every cost belongs in the same per-unit calculation.
Advertising cost
It is often useful to calculate contribution before advertising first. That gives you the margin available to fund PPC and helps estimate break-even ACOS.
Refunds and returns
For products with meaningful return or refund rates, use a realistic allowance rather than assuming every shipped unit becomes a perfect retained sale.
Other variable costs
Depending on the business, include any payment, prep, labelling, packaging or fulfilment-related cost that changes when another unit sells.
Separate fixed overheads
Software subscriptions, accountancy and general overheads still matter to the business, but keeping them separate from unit contribution can make product-level decisions easier to understand.
Recalculate when inputs change
A price increase, supplier change or fulfilment-fee update changes the economics immediately. Profit models should be living tools rather than one-time launch calculations.
See the CalcCommerce Amazon FBA Profit Calculator - UK for a downloadable spreadsheet covering unit profit, margin, break-even ACOS and price scenarios.
Try a quick calculation: use the free Amazon FBA Profit Margin Calculator, or use the downloadable UK profit workbook for repeat scenarios.
Independent seller resource. Not affiliated with or endorsed by Amazon. Check current fees and tax treatment for your business.