Ratio Calculator
How to use
- Pick Solve, Simplify or Scale.
- Solve: enter A, B and C to find the value that keeps A:B = C:D.
- Simplify: enter both sides to reduce them to the smallest whole numbers. Scale: multiply both sides by a factor.
How it works
Two ratios are equal when their cross products match: A × D = B × C, so D = B × C ÷ A.
To simplify, decimals are first turned into whole numbers, then both sides are divided by their greatest common divisor. 1920:1080 becomes 16:9.
Scaling multiplies both sides by the same factor, which keeps the ratio unchanged.
FAQ
How do I resize an image and keep its aspect ratio?
Use Solve with the original width and height as A and B, then the new width as C. The answer is the new height.
Can ratios contain decimals?
Yes. 1.5:2.5 simplifies to 3:5. The calculator scales decimals to whole numbers before reducing.
Why can A not be zero?
Solving divides by A. A ratio that starts with zero cannot be scaled to match a non-zero C.