About Percentage Guru
Percentage Guru exists because reverse percentages are the one piece of everyday arithmetic almost everyone gets wrong in the same way — by adding the percentage back instead of dividing it out. Every calculator here does that division correctly and shows its working.
Independent, and checked
Percentage Guru is an independent site, not part of any publisher or bank. No figure on it rests on anyone's word: every formula is enforced by the automated test suite described under corrections below, and errors, once reported, are fixed in the open.
What makes these calculators different
Every answer shows its check. The tool re-applies the percentage forwards and prints the result, so you can verify it without trusting us. Where rounding means the displayed figure will not reconcile to the penny, it prints ≈ rather than = instead of quietly hiding the difference.
The awkward cases are explained, not fudged. A 100% discount has no recoverable original, and plenty of calculators will happily print ∞ or an error code. This one explains why the answer does not exist.
It is fast because it is nearly nothing. Static HTML, system fonts, one small script, no ad networks, nothing that follows you around the web. The only measurement is Cloudflare's cookieless count of page views, plus Google Analytics if — and only if — you accept it; both are described in the privacy policy. Pages finish loading before most competitors have fetched their first banner.
The calculator never sends or saves what you type. Every calculation runs in your browser; there is no backend to receive it.
How it is paid for
Some pages may carry affiliate links to accounting software — always labelled, and disclosed at the top of any page where they are live. There may be modest display advertising later. Neither will ever sit inside a calculator or between a heading and its tool. Full detail is on the disclaimer page.
Corrections
The maths is covered by an automated test suite, including the edge cases most calculators get wrong. If you find an error in a figure, a rate or an explanation, please tell us — see contact.