Percentage Calculator

Five different questions all get called "percentage", and each has its own formula. Pick the wrong one and you get an answer that looks plausible but is wrong. The mode selector at the top of the form names each question in plain language so you can't pick one by accident.

The five modes

A few quick examples: 37 as a percentage of 160 is 23.13%. Going from 250 to 190 is a 24% decrease. Increasing 1,450 by 12% gives 1,624.00, and decreasing it by 12% gives 1,276.00.

Percentage change doesn't reverse

Going from 250 down to 190 is a 24% fall. Going back from 190 to 250 is a 31.58% rise. They differ because each one is measured against a different starting figure.

The increase and decrease modes have the same asymmetry. Add 12% to 1,450 and you get 1,624. Take 12% off 1,624 and you get 1,429.12, not 1,450. To undo an increase you divide by 1.12, and to undo a decrease you divide by 0.88. If you subtract the same percentage you'll reliably get the wrong number, and that's exactly how people get it wrong when removing tax from a gross figure.

It's also why a 50% fall needs a 100% rise to recover.

Zero denominators are rejected

Two of the modes divide by a value you supply, and zero has no sensible answer there.

Ask what 40 is as a percentage of 0 and you get an explanation instead of a number, because nothing is a percentage of zero. Ask for the change from 0 to 50 and you get the same, because any increase from nothing is undefined (it isn't infinite). Returning 0 for either would give you a specific false answer, so the tool shows no number at all.

Percent and percentage point are different words

The tool doesn't tell these apart, so you'll have to.

If an interest rate moves from 4% to 5%, that's a rise of one percentage point and also a rise of 25 percent. Both statements are true, and they describe the same event with very different force. Financial and political writing mixes them up all the time. When you're comparing two rates, subtract them for the percentage-point gap and use the percent change mode for the relative one. Then say which one you mean.

Where this page lives

The percentage calculator now sits under calculators instead of converters, which is where it always belonged. Its five modes cover the arithmetic behind most of the other tools on the site. Tax rates, discounts, margins, growth rates and interest are all percentage operations with their own labels.

Related growth and return tools

For percentage change applied to revenue across several years, use the revenue growth calculator. For a reduction off a price, with stacking explained, use the discount calculator. For profit expressed as a share of price rather than cost, use the profit margin calculator.