Percentage calculator
Work out a percentage of a number, a percentage change, or the value before one.
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About this tool
Answer the five percentage questions that come up in real work: what is 15% of 240, 30 is what percent of 240, what is the change from 240 to 300, increase 240 by 15%, and — the one most calculators leave out — what number a total came from before a percentage was added. Every answer comes with the sentence showing how it was worked out, so you can check it or explain it to someone else. It runs in your browser and needs no network connection.
Using this tool
How do I take tax back out of a total?
Use the last mode. If a total of 300 includes 25% tax, enter 300 and 25 and you get 240 — the figure before tax. Subtracting 25% from 300 gives 225, which is the mistake this mode exists to prevent.
Why is a change from zero rejected?
Because it has no answer. Percentage change divides by the starting value, and any increase from zero is infinite however you word it. Quote the absolute change instead: "up by 40 units", not "up by 4,000%".
Is a 50% rise followed by a 50% fall back where it started?
No, and this is the most common percentage error. 100 raised by 50% is 150; 150 cut by 50% is 75. Each percentage applies to a different base, which is why the reverse mode exists.
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