# Percentage Calculator - Percent Of, Percent Change, Increase and Reverse

> Free online percentage calculator: X% of Y, X as a percent of Y, increase and decrease, a value after a percentage change and the original behind it.

- URL: https://qilingtools.com/en/math/percentage
- Category: Math Tools (https://qilingtools.com/en/math)
- Tags: [Math](https://qilingtools.com/en/tags/math), [Finance](https://qilingtools.com/en/tags/finance)
- Last updated: 2026-10-26
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

The five everyday percentage questions in one place: what is 15% of 200, 30 is what percent of 120, how much did 80 grow to reach 100, what is a price after an 8% rise, and what number has 30 as its 15%. Each answer comes with the formula.

## How to use

1. Pick the kind of percentage question
2. Fill in the numbers
3. Read the answer and copy the working if you need it

## Features

- Percent of a number, ratio, change, increase/decrease and reverse percentage
- Formula shown for every result
- Works with decimals and negative numbers
- Live results, no button to press

## FAQ

### How do I calculate percentage change?

(new − old) ÷ old × 100%. Going from 80 to 100 is (100-80)/80 = 25%.

### What is the difference between percent and percentage points?

Percentage points are the absolute gap between two percentages: 3% rising to 5% is +2 percentage points, but a 66.7% increase.

### How do I work out a discounted price?

Use “Increase / decrease by %” with the discount percentage — 20% off 300 gives 240.

### How do I find the original price from the discounted one?

Use “Find the original value”: divide by the remaining percentage. If 80% of a price is 240, the original is 240 ÷ 80% = 300.

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