Percentage — the three formulas. This page shows the formula, a worked example and the assumptions behind the result.

How is percentage calculated?

The formula, a worked example and the assumptions are shown on this page. Results are estimates for planning, not financial, medical or legal advice.

Is this percentage calculator free to use?

Yes. It runs entirely in your browser, needs no account and stores nothing on a server.

Percentage Calculator

Three common percentage questions, answered instantly.

What do you want to find?

Percent (%)

Of number

Result

The three formulas

X% of a number: (percent ÷ 100) × number
Percent change: ((new − old) ÷ old) × 100 — negative means a decrease
What percent is X of Y: (X ÷ Y) × 100

Worked examples

25% of 80: (25 ÷ 100) × 80 = 20
Percent change from 50 to 65: ((65 − 50) ÷ 50) × 100 = 30% increase
What percent is 15 of 60: (15 ÷ 60) × 100 = 25%
A $200 item discounted 15%: 200 − ((15 ÷ 100) × 200) = 200 − 30 = $170

Percent change and percentage points are different things. Moving from 10% to 12% is a 20% increase, but a rise of 2 percentage points. Mixing the two is one of the most common errors in everyday reporting.