A calculator gives you the number. These explain which number to use, and why the obvious one is usually wrong.
Duty is not a percentage of what you paid the supplier. It is charged on a customs value that usually includes freight and insurance, and import VAT is then charged on top of the duty.
12 August 2026 · Import Duty Calculator UK, Import Duty Calculator USA, Landed Cost Calculator
Most people count postage and call it fulfilment. Add pick labour, packaging, the share of storage and the cost of returns, and the real figure is commonly half again as large.
12 August 2026 · Fulfillment Cost Calculator, Cost per Pick Calculator, Order Fulfillment Cost Calculator
Markup is measured against what you paid; margin against what you charged. A 50% markup is a 33.3% margin, and pricing to the wrong one quietly destroys profit at scale.
12 August 2026 · Markup vs Margin Calculator, Margin to Markup Converter, Wholesale Price Calculator
To take 20% VAT out of a gross price, divide by 1.2. Subtracting 20% instead is the single most common error in bookkeeping, and it understates the net figure by 4%.
12 August 2026 · Reverse VAT Calculator, VAT Calculator, Reverse Sales Tax Calculator
Almost every processor quotes one percentage and one fixed fee. On a £12 order the fixed part is the expensive half, and on an overseas sale two more charges appear that were never in the quote.
12 August 2026 · PayPal Goods and Services Fee Calculator, Stripe Fee Calculator, PayPal Reverse Fee Calculator