Percentage Calculator

Percentages come up constantly and are easy to get subtly wrong, particularly the ones that involve comparing two numbers rather than taking a share of one. This calculator covers the five distinct questions people actually mean when they say 'percentage', each in its own tab with its own inputs.

What is X% of Y answers the simplest case — a tip, a discount, a commission. X is what percent of Y turns two known numbers into a share, which is the calculation behind conversion rates and pass rates. Percentage change measures movement from an old value to a new one and is the right tool for growth, price rises and any before-and-after comparison.

Percentage difference is the one most often confused with change. Difference is symmetric: it compares two values against their average and gives the same answer whichever order you enter them. Change is directional and divides by the original value. Comparing this month against last month is a change. Comparing two suppliers' prices is a difference.

The fifth mode adds or subtracts a percentage from a starting value, which is the fastest way to apply a markup, a discount or a tax rate to a number in front of you.

Each mode shows the working, not just the answer, so you can check the logic before pasting the figure into a document. Results update as you type and every field accepts decimals and negative numbers.