Percentage Calculator

Five percentage calculations in one place: a percentage of a number, what percentage one number is of another, the change between two values, and adding or subtracting a percentage. Each one restates your question in words and shows the arithmetic, so you can confirm you asked what you meant to ask.

Why five modes instead of one box

Almost every percentage question people actually have is one of five, and they need different arithmetic. "What is 15% of 200" is a multiplication. "30 is what percent of 200" is a division. "What is the change from 200 to 250" needs the difference divided by the original. Adding and subtracting a percentage are different again.

Tools that offer a single input pair force you to work out which operation you need before you start, which is the part people get wrong. Choosing the question first, and having it restated in words above the inputs, removes that step.

The asymmetry that catches everyone

A 20% increase followed by a 20% decrease does not return you to where you started. Raise 100 by 20% and you have 120; cut 120 by 20% and you have 96. The percentages are equal but the bases are not, the rise was calculated on 100 and the fall on 120.

This matters in real situations. An investment that falls 50% needs to rise 100% to recover. A salary cut of 10% followed by a 10% rise leaves you 1% worse off. A product discounted 30% and then marked back up 30% is cheaper than it was. Whenever two percentage changes are applied in sequence, the order and the base determine the answer.

Percentage points versus percent

When the thing you are measuring is itself a percentage, the language matters. A central bank moving rates from 4% to 5% has raised them by one percentage point, but that is a 25% increase in the rate. Both statements are true and they sound wildly different.

Reporting frequently blurs this, usually in whichever direction makes the story bigger. If you are describing a change between two percentages, percentage points is the unambiguous unit. The change mode here guards against the mix-up automatically: whenever both numbers are small enough to be percentages themselves, the answer is spelled out in words with the points figure alongside the percent, so "from 40 to 50" reads as a 25% increase and 10 points in the same line.

Where the working helps

Every result comes with the arithmetic that produced it. That is partly so you can check it, and partly so you can reproduce it in a spreadsheet afterwards without having to remember which way round the division goes, which, for percentage change, is the detail most often inverted.

Nothing you enter is uploaded, logged or stored. The page is static and the calculation runs on your device.

The burger that failed because of a fraction

In the 1980s the A&W chain launched a third-pound burger to compete with the McDonald's Quarter Pounder: more meat, same price, and it won taste tests. It flopped. Focus groups later revealed why: many customers believed a third of a pound was smaller than a quarter, reasoning that three is less than four. The story comes from the chain owner's own memoir, and A&W later relaunched the burger, tongue firmly in cheek, as the 3/9 lb. burger. Fractions and percentages trip everyone eventually, which is what calculators are for.