How Ratio Calculator Works
To simplify a ratio, the tool finds the greatest common divisor (GCD) of both whole numbers using the Euclidean algorithm, then divides both sides by it. To find a missing value in an equivalent ratio A:B = C:?, it cross-multiplies and solves ? = (B × C) ÷ A.
How to Use This Tool
- Choose whether to simplify a ratio or solve for a missing value.
- For simplifying, enter both whole numbers of the ratio.
- For a missing value, enter A, B and C for the equation A:B = C:?.
- Select Calculate to see the result.
Example
Simplify: 24:36 reduces to 2:3. Missing value: if 2:3 = 10:?, then ? = (3 × 10) ÷ 2 = 15.
Helpful Tips
- Simplifying works on whole numbers — if your ratio has decimals, scale both sides up first (e.g. 1.5:2 becomes 15:20) before entering them.
- A simplified ratio like 2:3 means "for every 2 of the first thing, there are 3 of the second" — it doesn't tell you the actual quantities, only the proportion.
- The missing-value mode is handy for scaling recipes, mixing ratios, or resizing images proportionally.
Frequently Asked Questions
Does the simplify mode work with decimal numbers?
It's designed for whole numbers. For a ratio with decimals, multiply both sides by 10, 100, etc. until they're whole numbers, then enter those.
What if A and B share no common factor besides 1?
Then the ratio is already in its simplest form, and the tool will show it unchanged.
How does the missing-value mode work?
It assumes A:B is equivalent to C:?, and solves for the unknown using cross-multiplication: ? = (B × C) ÷ A.
Can A be zero when finding a missing value?
No — dividing by zero is undefined, so A must be a non-zero number for that mode.
This tool runs entirely in your browser. Your input is not uploaded to any server.