Ratio Calculator — Simplify a Ratio or Solve a Proportion
1920:1080 reduces to 16:9; 3:4 = 9:? solves to 12.
Runs on your device What you paste is processed by your own browser. It is never sent to a server, and it is not stored anywhere after you leave the page.
Short answer
A ratio can be simplified and a proportion solved for free in a web browser. A line such as 1920:1080 comes back reduced to its lowest terms, with the equivalent decimal and percentage; a line such as 3:4 = 9:? solves for the missing term, which may sit in any of the four positions. Ratios of three or more terms are reduced as well, and decimal terms are scaled up to whole numbers before the common factor is divided out, so 1.5:2 is 3:4.
At a glance
| Accepts | One ratio or proportion per line |
|---|---|
| Produces | The reduced ratio, or the solved proportion |
| Processing | In your browser |
| Price | Free, no limits |
| Account | Not required |
The two things a ratio gets asked about are the same question with and without a blank in it, so both live on one page: reduce 1920:1080 to 16:9, or fill the gap in 3:4 = 9:?. Which one a line is asking is visible from the line itself — the equals sign.
Decimals are handled by scaling rather than rounding. The terms are multiplied up to whole numbers first and only then divided by their greatest common divisor, so the reduced ratio is exactly equivalent to the one typed in rather than approximately so.
How to use it
- 1
Type a ratio or a proportion
16:9, 1920:1080, 2:3:4, or 3:4 = 9:? with the unknown written as ? or x. One per line.
- 2
Convert
A ratio comes back reduced; a proportion comes back solved and written out in full.
- 3
Read the equivalent forms
A two-term ratio also comes back as a decimal and as a percentage.
- 4
Copy the result
Copy to the clipboard, or download it as a text file.
Frequently asked questions
How do I mark the unknown term?
With ? or x, in whichever of the four positions it belongs to: 3:4 = ?:12 works as well as 3:4 = 9:?. Each line needs exactly one unknown.
Can it reduce a ratio of three or more terms?
Yes — 15:25:40 reduces to 3:5:8. The decimal and percentage rows appear only for two terms, because there is no single number that a three-term ratio is equal to.
Can the ratio be written with a slash?
Yes, 16/9 reads the same as 16:9. If what you have is a fraction you want as a mixed number or a percentage, the fraction simplifier is the closer tool.
What is this actually used for?
Aspect ratios, scale models and map scales, mixing concrete, paint or feed, splitting a bill or a profit share, and every "if 3 of these cost 4, what do 9 cost" question — which is the proportion form.