Free Percentage Calculator

Work out percentages three ways: a percent of a number, what percent one value is of another, and the percentage change between two numbers.

Percentage (%)

Number

Result

15% of 80 = 12

Quick answer

To find X% of a number, multiply the number by X ÷ 100. To find what percent A is of B, divide A by B and multiply by 100. To find the percentage change from an old value to a new value, subtract old from new, divide by the old value, then multiply by 100.

Formula & method

Percent of a number

result = number × (percent ÷ 100)

percent — the percentage you want, e.g. 15
number — the base value

What percent A is of B

percent = (A ÷ B) × 100

A — the part
B — the whole

Percentage change

change % = ((new − old) ÷ |old|) × 100

old — the starting value
new — the ending value

A positive result is an increase; a negative result is a decrease.

Examples

Example 1: 15% of 80

Input: percent = 15, number = 80
Result: 12
Why: 80 × (15 ÷ 100) = 80 × 0.15 = 12.

Example 2: 30 is what percent of 120

Input: A = 30, B = 120
Result: 25%
Why: 30 ÷ 120 = 0.25, and 0.25 × 100 = 25%.

Example 3: Price rises from 50 to 65

Input: old = 50, new = 65
Result: +30%
Why: (65 − 50) ÷ 50 = 0.30, and 0.30 × 100 = a 30% increase.

When to use this tool

Working out a tip, discount, sales tax, or commission.
Comparing growth between two figures, such as revenue, weight, or a test score.
Checking what share one number is of a total.

Common mistakes

Confusing “percent of” with “percent change.” 20% of 50 is 10, but a 20% increase on 50 is 60.
Dividing by the new value when finding percentage change — always divide by the original (old) value.
Assuming a 50% drop and a 50% rise cancel out. They don’t: 100 → 50 → 75.

Frequently asked questions

＋ How do I calculate a percentage of a number?

Divide the percentage by 100 to turn it into a decimal, then multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12.

＋ How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. For example, 30 out of 120 is (30 ÷ 120) × 100 = 25%.

＋ How do I calculate a percentage increase or decrease?

Subtract the old value from the new value, divide by the old value, and multiply by 100. A positive answer is an increase; a negative answer is a decrease.

＋ What is the difference between percent and percentage points?

A percentage point is the absolute gap between two percentages. Going from 10% to 12% is a rise of 2 percentage points, but a 20% relative increase.

＋ Why doesn’t a 50% increase cancel a 50% decrease?

Each percentage is taken from a different base. Starting at 100, a 50% drop gives 50; a 50% rise on 50 gives 75, not 100.

＋ Is my input sent to a server?

No. This calculator runs entirely in your browser, so the numbers you enter never leave your device.

✓ Free to use
✓ No sign-up required
✓ Runs entirely in your browser — nothing is uploaded.
✓ Formula and method shown above

Last updated: 2026-06-05How we calculate Report a correction Disclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.