Ratio to fraction converter
Fraction: enter A and B above.
Decimal: waiting on both numbers.
Percentage: waiting on both numbers.
Part-to-whole: waiting on both numbers.
Ratio to Fraction
Turn a ratio A:B into a fraction, a decimal, and a percentage, with the part-to-whole view shown alongside.
When is a ratio the same as a fraction?
A ratio A:B corresponds to the fraction A/B only when you are comparing the first part directly to the second part. That is the part-to-part reading, and it is what most people mean when they say "write the ratio as a fraction."
But if A and B are the two parts that make up a whole, then the whole is A + B, and the first part as a share of that whole is A/(A+B), not A/B. The converter above always shows both results, clearly labeled, so you can use the one that actually answers your question. Decimals in the input are handled honestly: both sides are scaled up by a power of ten to clear the decimal places, then reduced by the greatest common divisor.
Worked example: 3:5
- Part-to-part fraction: 3/5, already in lowest terms because 3 and 5 share no divisor.
- Decimal: 3 / 5 = 0.6.
- Percentage: 0.6 x 100 = 60%.
- Part-to-whole: the whole is 3 + 5 = 8, so 3/8 = 0.375 = 37.5%.
Notice the difference: 3 compared to 5 is 3/5, but 3 compared to the whole (3 + 5) is 3/8. Both are correct answers to different questions.
Related tools
Need to solve a full proportion instead of converting one? Theratio solver on the homepage fills in the missing value of A : B = C : D, and it also simplifies and scales ratios. Working with screen dimensions? Theaspect ratio calculator solves pixel widths and heights from a ratio.
Frequently asked questions
Is the ratio A:B the same as the fraction A/B?
Only when you mean part compared to part. The ratio 3:5 as a part-to-part comparison is the fraction 3/5. But if 3 and 5 are the two parts that make up a whole, the first part is 3/(3+5) = 3/8 of the whole, not 3/5.
Can I convert a ratio that has decimals?
Yes. Inputs like 1.5:2 are scaled up to whole numbers first (15:20), then reduced by the greatest common divisor, so you get the fraction 3/4.
How many decimal places do you show?
The decimal and percentage are rounded to 6 significant digits with trailing zeros trimmed, so 1:3 shows as 0.333333 and 33.3333%.
Is my data stored anywhere?
No. Everything runs locally in your browser with plain JavaScript. Nothing you type is sent to a server or saved.