200 15%-a = 30
(Documentation in English)
What it does
The Percentage Calculator solves the three everyday percentage problems in one place: X% of Y, X is what percent of Y, and the percentage change between two values. Switch modes with the segmented control, type two numbers, and read the answer instantly - no spreadsheet, no formula lookup.
Everything runs 100% client-side in your browser. Nothing you type is sent to a server, so it’s fine for rough sales figures or budgets, and the result updates live as you edit.
How to use it
- Pick a mode at the top: X% of Y, X is what % of Y, or % change A→B.
- Enter the first number under the left field (Percentage / Part / From).
- Enter the second number under the right field (Value / Total / To).
- Read the Result, then Copy it, or Copy share link to send the exact inputs to a teammate.
Examples
X% of Y
15% of 200 = 30
X is what % of Y
30 is 15% of 200
Percentage change (increase)
100 → 150 = +50%
Percentage change (decrease)
150 → 100 = -33.33%
Good to know
- Precision: results round to 2 decimals (e.g.
150 → 100shows-33.33%). - Edge cases: “X is what % of Y” with Y = 0, and “% change” from 0, are undefined and show a friendly note instead of an error.
- Shareable: your mode and both numbers are encoded in the URL (
?mode=of&a=15&b=200), so a link reproduces the exact view. - Private: all math is local - nothing leaves your browser.
- Related tools: JSON Formatter,
Base64Base64An encoding representing binary data as 64 safe ASCII characters, so it survives transport through text-only channels. It encodes — it does not encrypt.
Encode / Decode, Color Picker.