Startup Sums — ten calculators for starting a small business

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Startup SumsTen calculators for starting a small business, in the order you need them

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How to read these numbers. Every tool shows its formula, a worked example and the cases where it is wrong. The results are arithmetic on the numbers you type, not advice. They are not financial, tax or legal advice; tax rates in particular are your own estimate.

Nothing you type leaves your browser. The calculations run on your device and the numbers travel only in the web address, so you can bookmark or share a link to your results.

Rates and fees (Stripe, PayPal, Square, Etsy, eBay, Amazon, UK VAT) were read from the official pages on 5 October 2026 and are linked under each tool. They change; the fields are editable for that reason.

Who made this. [Your name], business and marketing background. Formulas checked against the sources listed under each tool. Found a mistake? hello@startupsums.com — corrections within 72 hours.