General

Percentage Calculator

Four percentage calculations in one place: a percentage of a value, one value as a percentage of another, percentage change, and percentage difference.

3 inputs Free, no sign-up

Your figures

In the first mode this is the percentage. In the others it is a plain number.

Try an example

Result

Your result

Enter your figures and the result appears here.

Estimates only. Rates, fees and specifications change. Confirm against the official source before you rely on a figure — see our disclaimer.

About this calculator

"Percentage" covers four different questions, and mixing them up is where the mistakes come from. Increase and decrease are not symmetric; percentage change and percentage difference are not the same thing. Pick the question you are actually asking and this calculator answers exactly that one.

How to use this calculator

  1. Choose the question you want answered.
  2. Enter your two values. In the first mode, A is the percentage and B is the amount.
  3. Read the result. The labels change to match the mode, so there is no ambiguity about which number is which.

The formula

What is A% of B?

Result = B x A / 100

A is what percentage of B?

Result = A / B x 100

Percentage change from A to B — measured against the starting value:

Result = (B - A) / |A| x 100

Percentage difference between A and B — measured against their average, so swapping the two values gives the same answer:

Result = |A - B| / ((|A| + |B|) / 2) x 100

Percentage change has a direction and a starting point. Percentage difference is symmetric and has neither. Going from 100 to 150 is a 50% increase; going from 150 back to 100 is a 33.3% decrease; the percentage difference between them is 40% either way.

SymbolMeaningUnit
A The first value, or the percentage in mode one
B The second value

Worked example

What is 18% of 2,500?

2,500 x 18 / 100 = 450

450 is what percentage of 2,500?

450 / 2,500 x 100 = 18%

Percentage change from 2,000 to 2,500

(2,500 - 2,000) / 2,000 x 100 = 25% increase

Notes and limits

  • A percentage increase followed by the same percentage decrease does not return you to the starting figure. Up 20% then down 20% leaves you 4% below where you began.
  • Percentage change needs a non-zero starting value. There is no meaningful percentage increase from zero, and the calculator says so rather than returning an error.
  • Percentage points and percentages are different. A rate moving from 5% to 7% is a rise of two percentage points, which is a 40% increase.

What this calculation assumes

  • Percentage change is measured against the starting value.
  • Percentage difference is measured against the average of the two values.

Frequently asked questions

What is the difference between percentage change and percentage difference?

Percentage change has a direction: it measures the movement from a starting value, so the order matters. Percentage difference is symmetric: it compares two values against their average, so swapping them gives the same answer. Use change for "before and after", difference for "how far apart are these two".

Why does a 20% increase then a 20% decrease not return to the original?

The decrease is calculated on the larger figure. 100 increased by 20% is 120; 120 decreased by 20% is 96, not 100. The two percentages are taken on different bases.

How do I calculate a percentage increase from zero?

You cannot. Percentage change is measured against the starting value, and dividing by zero has no answer. Report the absolute change instead.

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