🔢 Fraction to Percent Calculator

What is the Fraction to Percent Calculator?

A fraction and a percent are two ways of writing the same thing: a part of a whole. A fraction like 3/4 says you have 3 out of 4 equal parts. A percent says how many parts you would have out of exactly 100. Because both describe the same proportion, you can always move between them. To go from a fraction to a percent, you first turn the fraction into a decimal by dividing the top by the bottom, then multiply by 100.

So 3/4 becomes 3 divided by 4, which is 0.75, and 0.75 times 100 is 75 percent. The word percent literally means per hundred, which is why the multiply-by-100 step works: it rescales the proportion so the whole is 100. The same logic runs in reverse. To turn a percent into a fraction, you write the number over 100 and then reduce it. 75 percent is 75/100, and dividing top and bottom by their greatest common divisor (25) gives 3/4.

The one input that breaks the method is a denominator of zero. A fraction such as 5/0 is undefined, because dividing by zero has no meaning in arithmetic: there is no number you could multiply by zero to get 5. This calculator detects a zero denominator and tells you the result is undefined rather than showing a misleading figure. Some fractions, like 1/3, also produce a repeating decimal (0.3333...), so the percent (33.33%) is a rounded value rather than an exact one.

When to use it

• Converting test or quiz scores written as a fraction (such as 18/20) into a percentage grade.
• Turning a recipe or ingredient ratio into a percentage to scale it up or down.
• Reading a statistic given as a fraction and expressing it as a more familiar percent.
• Doing the reverse: converting a discount or interest percent back into a simple fraction.

How to use the Fraction to Percent Calculator

1. Keep the calculator in "Fraction to percent" mode (the default).
2. Enter the numerator (the top number of the fraction).
3. Enter the denominator (the bottom number). If it is 0, the result is undefined.
4. Read off the percent, the reduced fraction, and the decimal, with the steps shown below.
5. To convert the other way, click "Percent to fraction" and type a percentage instead.

Formula & method

Worked examples

Common fractions with their decimal and percent equivalents

Common mistakes to avoid

• Forgetting to multiply by 100. Dividing the fraction gives you the decimal, not the percent. 3/4 is 0.75 as a decimal, but the percent is 0.75 x 100 = 75%. Skipping the times-100 step leaves you with the wrong figure.
• Dividing in the wrong order. Always divide the numerator (top) by the denominator (bottom), not the other way round. 1/4 means 1 / 4 = 0.25, while 4 / 1 = 4 would give a completely different answer.
• Treating a zero denominator as valid. A fraction like 5/0 is undefined because you cannot divide by zero. There is no real percentage for it, so the calculator flags it rather than returning a number.
• Rounding a repeating decimal too early. Fractions such as 1/3 give a never-ending decimal (0.3333...). The percent (33.33%) is rounded, so be aware that three of them add to 99.99%, not exactly 100%, unless you keep the exact fraction.

Glossary

Numerator

The top number of a fraction, showing how many parts you have.

Denominator

The bottom number of a fraction, showing how many equal parts make up the whole. It cannot be zero.

Percent

A proportion expressed out of 100. The word means "per hundred", so 50% is 50 out of every 100.

Decimal

A way of writing a fraction using place value after a point, such as 0.75 for three quarters.

Greatest common divisor

The largest whole number that divides two numbers exactly, used to reduce a fraction to lowest terms.

Frequently asked questions