Practical tools for the arithmetic of running a business

Why this site exists

Most small business owners do not need a spreadsheet, an enterprise finance package or a two-hour webinar. They need to know what £1,200 including VAT is without VAT, what price to charge to keep a 35% margin, or how many billable hours a £45,000 income actually requires. Those questions come up weekly, and the answers need to take seconds.

So the tools here are deliberately narrow and deliberately plain. One job per page. Big inputs, a clear result, and the working shown underneath so you can trust it or check it. No account, no paywall, no fifteen-field onboarding form before you can see a number.

How the calculators are built

Each calculator is a pure arithmetic function with a published formula. The formulas are tested against worked examples that also appear on the page, so the documentation and the code cannot drift apart without someone noticing. Currency is handled in pounds sterling to two decimal places, which is how invoices are presented.

Tax rates and thresholds are stored separately from the calculation logic, in one file, with the tax year labelled on the page. That means a rate change is a one-line update rather than a rewrite — and it means we can be honest that a rate you read in an article may already have moved.

What this site is not

• It is not accountancy or tax advice. We do not know your scheme, your sector or your transactions. For anything with a real consequence, use a qualified adviser.
• It is not affiliated with HMRC or GOV.UK. No calculator here is approved or accredited by HMRC, and we do not claim otherwise.
• It is not accounting software. The invoice generator builds a document. It does not store an invoice history, file a VAT return or keep your records.

Editorial standards

• British English, pounds sterling and UK terminology throughout.
• No invented statistics, customer numbers, testimonials or ratings — there are none on this site.
• Tax and legal statements link to the primary GOV.UK or HMRC page they are based on, so you can check them directly.
• Corrections are published, not quietly patched. If you report an error and we fix it, the page's updated date changes.

How the site is funded

The tools are free. At the time of writing there is no advertising on the site and no affiliate or partnership arrangement with any software provider, bank or adviser. If we introduce either, it will be clearly labelled where it appears and set out in the affiliate disclosure. It would never change a calculation, gate a tool, or buy a recommendation.

Something wrong?

Tell us. A reported calculation error is the most useful message this site can receive — use the contact form and choose “Report a calculation error”, including the figures you entered and the result you expected.