# Percentage Calculator

> The Percentage Calculator is a free everyday percentage tool in the SoapBox tools suite. It gathers the common percentage questions people actually ask into one small page, with the answer updating…

Canonical: https://wiki.soapbox.community/wiki/Percentage_Calculator
Section: Tools
Last updated: 2026-10-20
Publisher: Library of Ashurbanipal (Van Kush Family Research Institute), https://wiki.soapbox.community

The **Percentage Calculator** is a free everyday percentage tool in the SoapBox tools suite. It gathers the common percentage questions people actually ask into one small page, with the answer updating as the numbers are typed.

## What it does

- **X% of Y** — for example, 15% of 200 is 30.
- **X is what % of Y** — 30 is 15% of 200.
- **Percentage change** — the increase or decrease from one number to another (200 to 250 is +25%).
- **Add a percent** — increase a number by a percentage.
- **Subtract a percent** — decrease a number by a percentage, such as a discount.
- **Tip splitter** — a tip percentage on a bill, with the total and the amount per person when split several ways.

## How to use it

Pick the question from the tabs, type the numbers, and the result appears immediately. It runs entirely in the browser; no account is required and nothing is sent anywhere. A JSON API is available at /api/pct for programmatic use.

## See also

- SoapBox Tools
- Unit Price Calculator
- Soap Calculator

## Sources

- Standard arithmetic; no external data source.

## Coverage

Describes the SoapBox Percentage Calculator and its six modes (percent of, is-what-percent, percentage change, add/subtract percent, and a tip splitter).