Ratio Calculator
Simplify ratios and solve proportions for a missing value.
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How it works
In simplify mode, the calculator divides both terms of a ratio by their greatest common divisor (via the Euclidean algorithm) to reduce it to lowest terms — so 18:24 becomes 3:4. In proportion mode it solves A:B = C:x (or any missing term) by cross-multiplication, finding the value that keeps the two ratios equal. This is the math behind scaling recipes, resizing images, and converting units. Everything runs locally in your browser with exact arithmetic.
A : B = C : x → x = (B × C) / A
Common use cases
- Scaling a recipe up or down while keeping ingredient ratios.
- Resizing an image or layout to a target proportion.
- Reducing an aspect ratio like 1920:1080 to 16:9.
Frequently asked questions
How does proportion solving work?
Given three of the four terms in A:B = C:x, the missing one is found by cross-multiplication. For example, to find x in 2:3 = 8:x, multiply 3 × 8 and divide by 2 to get 12.
Can it reduce a ratio like 1920:1080?
Yes. Simplify mode divides both numbers by their greatest common divisor, turning 1920:1080 into 16:9.
Does it work with decimals?
Proportion solving accepts decimals. Simplify mode is designed for whole-number ratios, since reducing by a common divisor only applies to integers.