Ratio Calculator
The Ratio Calculator does two jobs.
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In simplify mode it reduces a ratio like 1920:1080 to its lowest whole-number terms (16:9) and shows the decimal and percentage. In proportion mode it solves A : B = C : D for whichever term you leave blank, using cross-multiplication.
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Add this tool to your website with customizable styling
How to Use
Choose a mode
Pick Simplify to reduce a ratio, or Solve proportion to find a missing term in A : B = C : D.
Enter your numbers
Type the two terms of the ratio, or three of the four proportion terms โ decimals are allowed.
Leave one blank
In proportion mode, leave exactly one of the four boxes empty; that is the value the calculator solves for.
Read and copy
See the simplified ratio with its decimal and percentage, or the solved value, then copy it with one click.
Frequently Asked Questions
How do you simplify a ratio?
Divide both sides of the ratio by their greatest common divisor. For example 1920 and 1080 share a divisor of 120, so 1920:1080 simplifies to 16:9. This tool does that automatically, including for decimal inputs, which it first scales up to whole numbers.
What is a proportion and how is it solved?
A proportion states that two ratios are equal, written A : B = C : D. Cross-multiplication gives A ร D = B ร C, so any one missing term can be found from the other three. Leave one box blank and the calculator solves it.
Can I use decimals?
Yes. Both modes accept decimal numbers, and you can use either a dot or a comma as the decimal separator. Ratios with decimals are scaled to whole numbers before being reduced.
Does it work for aspect ratios?
Yes โ that is one of the most common uses. Enter a pixel width and height (for example 1920 by 1080) in simplify mode to get the aspect ratio (16:9), along with the exact decimal (1.7778).