# Percentage Calculator

> X% of Y = X ÷ 100 × Y, so 15% of 240 is 36, 45 is 75% of 60, and going from 80 to 100 is a (100 − 80) ÷ 80 × 100 = 25% increase. The calculator also finds percentage difference, adds or removes a percentage, and recovers the original number.

- Interactive calculator: https://calculatorswithsteps.com/percentage-calculator
- Category: Math & Statistics Calculators
- Last updated: 2026-11-10
- Publisher: Calculators With Steps (calculatorswithsteps.com)

## How to use the percentage calculator

Choose the question that matches your problem from the drop-down, then type your two numbers. The answer and the step-by-step working update immediately.

| You want to know | Choose | Example |
| --- | --- | --- |
| A percentage of an amount | What is X% of Y? | 15% of 240 = 36 |
| Marks, attendance or a share as a % | X is what percent of Y? | 45 of 60 = 75% |
| How much something grew or fell | Percentage increase / decrease | 80 → 100 = +25% |
| How far apart two values are | Percentage difference | 40 vs 50 = 22.2% |
| A price with tax, tip or markup | Add or subtract a percentage | 500 + 18% = 590 |
| The total before a percentage | X is P% of what number? | 30 is 20% of 150 |

## Percentage formulas

A percentage is a number out of 100. The word comes from the Latin *per centum*, "by the hundred". Every percentage problem comes down to the same relationship:

**Part = Percentage ÷ 100 × Whole**

Rearrange it to solve for whichever value you are missing:

- **Part** = P ÷ 100 × Whole
- **Percentage** = Part ÷ Whole × 100
- **Whole** = Part ÷ (P ÷ 100)
- **Percentage change** = (New − Old) ÷ |Old| × 100
- **Percentage difference** = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100

## Worked examples

**Exam marks.** You scored 432 out of 500. 432 ÷ 500 = 0.864, and 0.864 × 100 = **86.4%**. To convert a CGPA rather than raw marks, use the [CGPA to percentage calculator](https://calculatorswithsteps.com/cgpa-to-percentage-calculator).

**Salary hike.** Your pay rose from 52,000 to 57,200. The change is 5,200, and 5,200 ÷ 52,000 × 100 = **10% increase**.

**Sale price.** A 1,299 item is 30% off. 1,299 × (1 − 0.30) = **909.30**. The [discount calculator](https://calculatorswithsteps.com/discount-calculator) also shows how much you save.

**Reverse GST or sales tax.** A bill of 1,180 includes 18% tax. The pre-tax amount is 1,180 ÷ 1.18 = **1,000**. A common mistake is subtracting 18% of 1,180, which gives 967.60, the wrong answer.

## Common percentage mistakes

- **Increases and decreases are not symmetric.** A 50% fall followed by a 50% rise does not get you back to where you started: 100 → 50 → 75. To undo a 50% drop you need a 100% gain.
- **Percentage points are not percent.** If an interest rate rises from 4% to 5%, it went up by 1 percentage point, which is a 25% relative increase.
- **Use the right base.** "Percent of" always divides by the whole, and "percent change" always divides by the original value, never the new one.
- **Stacked discounts multiply.** 20% off and then another 10% off is a 28% total discount, not 30%, because 0.8 × 0.9 = 0.72.

## Quick mental-math tricks

- 10% of any number: move the decimal point one place left (10% of 340 = 34).
- 5% is half of 10%, and 1% means moving the decimal point two places left.
- 15% = 10% + 5%, which is handy for tipping (15% of 60 = 6 + 3 = 9).
- Percentages are reversible: 8% of 50 equals 50% of 8, which is 4.
- 25% is a quarter, 50% is a half and 75% is three quarters.

## Where percentages show up

Percentages appear in school grades and attendance requirements (many Indian colleges require 75%), interest rates and investment returns, inflation figures, tax and GST, discounts and tips, nutrition labels and statistics in the news. Knowing which formula to use, and which number is the base, is what keeps the answer right.

## Frequently asked questions

### How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For example, 15% of 240 is 0.15 × 240 = 36.

### How do I work out what percent one number is of another?

Divide the part by the whole and multiply by 100. If you scored 45 out of 60, that is 45 ÷ 60 × 100 = 75%.

### What is the formula for percentage increase?

Percentage increase = (new value − original value) ÷ original value × 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%. If the result is negative, it is a percentage decrease.

### What is the difference between percentage change and percentage difference?

Percentage change measures movement from an original value to a new one, so it divides by the original. Percentage difference compares two values where neither is the starting point, so it divides by their average. From 40 to 50 is a 25% increase, but the percentage difference between 40 and 50 is 22.2%.

### How do I calculate attendance percentage?

Divide the classes you attended by the total classes held and multiply by 100. Attending 68 of 80 lectures gives 68 ÷ 80 × 100 = 85%. Use the 'X is what percent of Y' option above.

### How do I add a percentage to a number, such as tax or a markup?

Multiply the number by (1 + percentage ÷ 100). Adding 18% to 500 gives 500 × 1.18 = 590. To remove a percentage, multiply by (1 − percentage ÷ 100).

### How do I find the original number before a percentage was applied?

If you know a part and the percentage it represents, divide the part by the percentage as a decimal. If 30 is 20% of a number, the number is 30 ÷ 0.20 = 150.

## Sources

- [Percentage – Wikipedia](https://en.wikipedia.org/wiki/Percentage)
- [Relative change and percentage difference – Wikipedia](https://en.wikipedia.org/wiki/Relative_change)