How to Calculate a Percentage

To find X% of a number, multiply the number by X/100. To find what percent one number is of another, divide the first by the second and multiply by 100. A calculator does it instantly.

Last updated: 2026-07-17

Open Percentage Calculator →Open Discount Calculator →

The three percentage questions

Most percentage problems are one of these:

What is X% of Y? Multiply: 20% of 150 = 150 × 0.20 = 30.
X is what percent of Y? Divide and ×100: 30 is 30 ÷ 150 × 100 = 20%.
Percentage change from A to B? (B − A) ÷ A × 100. From 150 to 180 = 30 ÷ 150 × 100 = 20% increase.

Do it instantly

Skip the mental maths with the Percentage Calculator — enter the numbers and it handles all three cases.

Everyday examples

Tax: add 8% sales tax to a $50 item → 50 × 1.08 = $54.
Discount: 25% off $80 → 80 × 0.75 = $60. The Discount Calculator shows the final price directly.
Tip, interest, grades — all the same formulas.

Private

Calculations run in your browser — nothing is sent anywhere.

Frequently asked questions

How do I calculate a percentage increase?

Subtract the old value from the new value, divide by the old value, then multiply by 100. From 150 to 180 is (180−150)/150 × 100 = 20%.

How do I find what percent one number is of another?

Divide the first number by the second and multiply by 100. For example, 30 out of 150 is 30/150 × 100 = 20%.

Tools used in this guide

Percentage Calculator

Work out percentages, increases and decreases.

Discount Calculator

See the final price after a discount.