Why doesn’t a 20% fall cancel out a 20% rise?

Each percentage is taken from a different base. Raising 100 by 20% gives 120, and 20% of 120 is 24, so the fall lands on 96 rather than back at 100. Undoing a 20% increase takes a 16.67% decrease. It is the same arithmetic that makes stacked discounts add up to less than they look like they should.

Why won’t it show a change starting from zero?

Any rise from zero is infinite in percentage terms, so that card says so instead of a number.

Percentage Calculator

No upload · runs in your browser

What is X% of Y?

Percentage%Of value

Result

15 ÷ 100 × 240 = 36

X is what percent of Y?

This valueOut of

Result

25%

45 ÷ 180 × 100 = 25%

Increase or decrease between two numbers

FromTo

Result

25% increase

A difference of 30

(150 − 120) ÷ 120 × 100 = 25%

Add or subtract a percentage

ValuePercentage%

Direction

Result

2,950

Markup of 450

2,500 × (1 + 18 ÷ 100) = 2,950

Every result is computed on your device as you type, no numbers are uploaded.

How it works

Percentage Calculator: Percent Of, Change, Markup

Four percentage calculators on one page. Each updates as you type and shows the formula it used, so you can copy the working as well as the answer.

What this does

All four calculators on screen at once, updating as you type
The arithmetic printed under each result, ready to copy into your working
Change measured against the absolute starting value, so a negative base still reads correctly

FAQ

A percentage change is relative to the starting number, so 40 rising to 50 is a 25% increase. Percentage points measure the plain gap between two percentages, so 40% rising to 50% is a rise of 10 percentage points. Reported statistics mix the two up constantly, and the second card here, “X is what percent of Y”, is the one that answers the relative question.

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