About This Calculator
percentdecreasecalculator.org is a free online tool for working out percentage decreases between any two values. Type a number, see the answer. There is no submit button, no signup, and no tracking beyond standard server logs and aggregate analytics. The site exists because the underlying math comes up constantly, in retail, in finance, in science, in everyday budgeting, and most people prefer a clean, predictable tool over a search-engine snippet that might or might not show the right formula.
Every calculator on the site updates as you type. Outputs use plain English labels and clear units. The formula sits underneath each calculator so the answer is never a black box. The reference chart and the worked examples page cover the cases where you would rather look up the answer than compute it. Specialized pages for discounts, growth rate, and population change, plus fixed-rate calculators for 5%, 10%, 15%, 20%, 25%, 30%, and 50%, handle the recurring questions readers ask in their own words.
Accuracy is built in. The calculations follow the standard mathematical definitions set out on the formula page: percentage decrease, percentage increase, percentage change, percentage difference, compound annual growth rate, and stacked discount multipliers. Edge cases are handled deliberately. Negative starting values, division by zero, and very large numbers all produce sensible output or a clear placeholder instead of an error.
Who This Site Is For
Students checking homework, shoppers comparing a sale price against the sticker price, analysts building a quick sanity check before a report goes into a spreadsheet, and anyone who just wants a straight answer without opening a full spreadsheet program. The site is built to answer one question well rather than many questions poorly, so each calculator focuses on a single, specific calculation with its own worked examples and its own plain-English explanation.
Why It's Free
The site runs on a small, fast, static hosting setup with no server-side database, so the running cost is low enough that the site can stay free and ad-light indefinitely. There is no premium tier, no paywall on any calculator, and no limit on how many times you can use a tool in a day.
Built for Every Device
Every page is designed mobile-first: inputs are large enough to tap accurately, text stays readable without zooming, and tables scroll horizontally instead of squeezing off-screen. The same calculators work identically on a phone, a tablet, a laptop, or a shared classroom computer.
Available in 19 Languages
The homepage is fully translated into Spanish, French, German, Portuguese, Italian, Dutch, Russian, Chinese, Japanese, Korean, Arabic, Hindi, Turkish, Polish, Swedish, Norwegian, Danish, and Finnish, in addition to English. Each translated version carries the same formula, the same worked examples, and the same depth of explanation, not a shortened summary.
The site is open access. Use it on your phone, your laptop, in a classroom, or at a register. No part of it requires an account or stores what you type into a calculator. If you spot a mistake or want a new calculator added, the Contact page is the place to write in.