About the Percent Converter
Percentages, decimals and fractions are three ways of writing the same ratio, and per mille and parts per million are the same idea for smaller amounts. This percent converter takes a value in any one of these forms and shows it in all the others at once: 37.5 percent is 0.375, 3/8, 375 per mille and 375,000 ppm. Fractions are found as the simplest fraction with a bottom number up to 10,000. You can also type a mixed number such as 1 3/8. It is a quick way to move between the forms when doing homework, recipes, discounts, chemistry concentrations or spreadsheets.
Updated October 2026
How to use the Percent Converter
- 1Choose what kind of value you have: percent, decimal, fraction, per mille or ppm.
- 2Type the value. For fractions, write 3/8 or a mixed number like 1 3/8.
- 3Read the same amount in every other form.
- 4Copy the result with the Copy result button.
A quick reference
- 1/2 = 0.5 = 50%
- 1/4 = 0.25 = 25%; 3/4 = 0.75 = 75%
- 1/3 = 0.3333… = 33.33…%
- 1/8 = 0.125 = 12.5%
- 1% = 0.01 = 10 per mille = 10,000 ppm
Picking the best form
Percentages are easy to compare and understand at a glance, which is why they are used for discounts, scores and statistics. Decimals are what calculators and spreadsheets use. Fractions are exact for numbers like one third that decimals can only approximate. Per mille and ppm make tiny amounts readable: 0.0005 is 0.05 percent, 0.5 per mille or 500 ppm.
More percentage tools
The Percentage Calculator finds a percent of a number or the change between two numbers, the Fraction Calculator does arithmetic with fractions, the Decimal to Fraction Converter focuses on decimals, the Ratio Calculator scales ratios and the Discount Calculator applies percentages to prices. The ppm Converter covers concentration units in more detail.
Features
- Percent, decimal, fraction, per mille and ppm together
- Simplest fraction for any decimal
- Mixed numbers accepted as input
- Negative values and values over 100%
- Exact fractions flagged, close ones marked as about
- Copy in one tap
- Runs in your browser
Frequently asked questions
How do I convert a percent to a decimal?
Divide by 100, which moves the decimal point two places to the left. 37.5 percent becomes 0.375, and 5 percent becomes 0.05. To go back, multiply the decimal by 100.
How do I convert a percent to a fraction?
Write the percentage over 100 and simplify. 25 percent is 25/100, which simplifies to 1/4. For 37.5 percent, write 37.5/100, multiply top and bottom by 10 to get 375/1000 and simplify to 3/8. The tool does this automatically.
How do I convert a fraction to a percent?
Divide the top number by the bottom to get a decimal, then multiply by 100. For 3/8 you get 0.375, which is 37.5 percent. For mixed numbers such as 1 1/2, convert to 1.5 first, giving 150 percent.
What is per mille?
Per mille, written ‰, means parts per thousand. 5 per mille is 0.5 percent. It is used for some tax rates, alcohol levels in blood and salinity of sea water.
What does ppm mean and how do I convert it?
Parts per million is one part in 1,000,000. To convert ppm to percent, divide by 10,000: 250 ppm is 0.025 percent. To convert percent to ppm, multiply by 10,000. It is used for tiny concentrations like chemicals in water.
Why does a fraction say about?
Some decimals, such as 0.333333 typed to six places, are not exactly a simple fraction. The tool finds the closest simple one and marks it about when the match is not exact. Typing 33.3333333333 percent gives 1/3.