How to Convert a Decimal to a Percent (and a Percent to a Decimal)

Published 2026-10-25

Decimals and percents are two ways of writing the same thing. 0.25 and 25% both mean a quarter. Once you see that a percent is just “per hundred”, converting between them takes one step in either direction.

Decimal to percent: multiply by 100

To turn a decimal into a percent, multiply by 100 and add the % sign. In practice, that means moving the decimal point two places to the right.

When there aren’t enough digits, add zeros: 0.6 becomes 0.60, which becomes 60%. A decimal bigger than 1 gives a percent over 100%, which is normal for things like growth: 1.5 times as many is 150% of the original.

Percent to decimal: divide by 100

Going the other way, divide by 100, which means moving the decimal point two places to the left and dropping the % sign.

• 45% → 0.45
• 8% → 0.08
• 12.5% → 0.125
• 0.5% → 0.005
• 200% → 2

You need this step whenever a percent goes into a formula. A 6.5% interest rate is 0.065 in a loan formula, and a 7% sales tax means multiplying a price by 0.07.

Fraction to percent

Divide the top number by the bottom number to get a decimal, then multiply by 100.

• 3/8 = 3 ÷ 8 = 0.375 = 37.5%
• 2/5 = 0.4 = 40%
• 1/3 = 0.333… ≈ 33.3%

A few are worth remembering because they come up all the time: 1/2 = 50%, 1/4 = 25%, 3/4 = 75%, 1/5 = 20%, 1/10 = 10%.

What percentage is X of Y?

This is the same idea in a different form. Divide the part by the whole, then multiply by 100.

• 18 correct answers out of 24: 18 ÷ 24 = 0.75, so 75%.
• 45 minutes out of an hour: 45 ÷ 60 = 0.75, so 75%.
• $12 saved on a $80 jacket: 12 ÷ 80 = 0.15, so 15% off.

The order matters. The “whole” is the number you’re comparing against, and it always goes on the bottom. The percentage calculator handles this and the other common percent questions, including percent change between two numbers.

Common mistakes

• Moving the point the wrong way. A quick check: a percent number is always 100 times bigger than its decimal. If 0.08 turned into 0.0008%, the point went the wrong way.
• Treating 0.5% as 50%. 0.5% is half of one percent, which is 0.005 as a decimal. This matters with interest rates and fees.
• Mixing up percent and percentage points. If a rate goes from 4% to 6%, it rose 2 percentage points, but that’s a 50% increase in the rate itself.
• Adding percents that apply one after another. 20% off and then another 10% off is 28% off in total, not 30%, because the second discount applies to the already-reduced price. The discount calculator works out stacked discounts for you.

Quick reference

For working out percentages without a calculator, see our six mental math tricks for percentages.