Percentage calculator

Work out percentages, shares and changes instantly — three calculations on one screen, no button, nothing uploaded.

Percentage

Of this number

Part

Whole

From

How to use it

Three calculations sit on one screen. Fill in the two boxes for the one you need — the result appears as you type, with no button to press.
“What is a percentage of a number” gives the amount: 25% of 200 is 50.
“What percentage is one number of another” gives the rate: 50 is 25% of 200.
“Percentage change” tells you the rise or fall from one number to another: 200 → 250 is a +25% increase.
Copy a result with its button, or use “Download .txt” to save just the value.

25% of 200

25% of 200 = 50 because 25/100 × 200 = 50. The same screen also shows that 50 is 25% of 200, and that going from 200 to 250 is a +25% increase.

Three everyday operations only: a percentage of a number, one number as a percentage of another, and percent change. No tips, compound interest or running totals.
Loose number input: type a % sign if you like (it is ignored), and thousands separators (1,234.5) are accepted. A period, full-width period or Arabic decimal mark is the decimal point; a comma is only a thousands separator.
Digits may be typed as ASCII 0–9, Arabic-Indic ٠–٩, Persian ۰–۹ or full-width ０–９; bidirectional marks and spaces are ignored. The output is always plain Latin digits with a period decimal and a % sign.
Honest errors: a non-number or two decimal points is rejected with a message, and a zero in the “whole” or “from” box is reported instead of showing NaN.
Nothing is uploaded, stored or put into the URL: no history, no share link carrying the value. Everything runs in your browser.

What people usually need next, once they have the percentage they wanted.