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Percentage calculator

Four percentage calculations in one: X% of Y, what percent X is of Y, and increasing or decreasing a value by a percentage.

Related tools

All Percentages & ratios tools →
Percentage change calculatorFind the percentage increase or decrease between two numbers.Percentage decrease calculatorHow far a value fell from an old figure to a new one, as a percentage — and the absolute drop. A negative result means it actually rose.Percentage difference calculatorCompute the percentage difference between two values (relative to their average).Percentage error calculatorCompute the percentage error between a measured and a true value.Percentage increase calculatorBy how much a value grew from an old figure to a new one, as a percentage — and the absolute change. A negative result means it actually fell.Percentage point change calculatorFind the difference in percentage points between two percentages, and the relative change.Reverse percentage calculatorFind the whole when you know that a value is a given percentage of it.Ratio calculatorSimplify a ratio to its lowest terms and see it as a decimal.

The Percentage calculator turns Calculation, First number (①), Second number (②) into Result, instantly and for free. For instance, with Calculation = ① % of ②, First number (①) = 15 and Second number (②) = 200 it returns Result = 30.

How to use it

  1. Enter your values: Calculation, First number (①), Second number (②).
  2. Read the result instantly: Result.

Frequently asked questions

What does the Percentage calculator actually compute?

It takes Calculation, First number (①) and Second number (②) and derives Result from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

3 values: Calculation, First number (①) and Second number (②). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Calculation = ① % of ②, First number (①) = 15 and Second number (②) = 200, the calculator returns Result = 30. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

Which “Calculation” option should I choose?

You can pick between « ① % of ② », « ① is what % of ② », « ① increased by ② % » and « ① decreased by ② % ». Each one changes what the calculator works out, so switch and compare — the default is « ① % of ② ».

When would I actually use this?

The everyday cases: a discount at the till, a rise or fall between two figures, the price before tax, and working backwards from a total.

What is the most common mistake?

Undoing a percentage by applying it again. Take 20% off 100 and you get 80; add 20% to 80 and you get 96, not 100 — the two operations use different bases.

What is the difference between the Percentage calculator and the Percentage change calculator?

This one returns Result; the Percentage change calculator returns Change and Difference. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Percentage decrease calculator is the closest one after this: How far a value fell from an old figure to a new one, as a percentage — and the absolute drop. A negative result means it actually rose.

What else is worth having open alongside it?

Percentage difference calculator and Percentage error calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from, and how current are they?

Percentage arithmetic is exact and universal. Where a result is a rate rather than an amount, the tool states the base it was taken on, because that is where the ambiguity lives.

Further reading

All guides →
How-toHow to Calculate a Percentage: 4 Methods with ExamplesA clear guide to percentages: find X% of a number, work out what percent one number is of another, and add or subtract a percentage — with worked examples.ExplainerPercentage Points Are Not PercentMoving from 4% to 5% is a rise of one percentage point and a rise of twenty-five percent. Both statements are true, which is exactly why the ambiguity is so easy to exploit — and why basis points exist.ExplainerStacked Discounts Do Not Add UpTwenty percent off and then a further ten percent off is not thirty percent off — it is twenty-eight, because the second discount applies to the already-reduced price. The general rule, the cases where order matters, and how sales tax changes the answer.How-toPercentage Change: Increase and DecreaseSubtract old from new, divide by the old value, times 100. Here's the formula, why increases and decreases aren't symmetric, and where it's used.How-toHow to Simplify a RatioDivide both sides by their greatest common divisor. Here's what a ratio is, how to reduce it, why units must match first, and how to compare ratios.How-toLCM and GCD ExplainedThe GCD is the biggest shared divisor; the LCM is the smallest shared multiple. Here's what each means, how to find them with prime factors, and the shortcut linking them.