How to Calculate Percentages (With Examples)

Finding X% of a number

Multiply the number by the percentage and divide by 100. For example, 20% of 150 = 150 × 20 ÷ 100 = 30. A quick mental trick: 10% is the number with the decimal moved one place left (15), so 20% is double that (30).

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’s 45 ÷ 60 × 100 = 75%. This is the calculation you use for test scores, completion rates and shares of a total.

Percentage increase and decrease

Subtract the old value from the new value, divide by the old value, then multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25%. A negative result means a decrease. Our calculator handles all three of these instantly.

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