Ratio Calculator
A ratio calculator simplifies a ratio (like an aspect ratio or mixing ratio) to its lowest whole-number terms using the greatest common divisor, and separately solves proportions of the form A:B = C:? for the missing fourth value via cross-multiplication. A simplified ratio and its original form describe the exact same relationship — 4:8 and 1:2 are interchangeable — which is why reducing to lowest terms does not lose any information, it just states the same proportion with the smallest possible whole numbers.
How it works
- To simplify, enter two positive whole numbers and read the reduced ratio.
- To solve a proportion, enter A, B, and C in "A:B = C:?" and read the missing value.
Formula Simplify: divide both parts by their GCD. Proportion: D = C × B / A
Frequently asked questions
What is a real example of simplifying a ratio?
A 1920×1080 screen resolution simplifies to a 16:9 aspect ratio — the same math used here.
What is a proportion used for?
Scaling a recipe, converting a scale-model measurement to real size, or finding an unknown quantity that keeps the same ratio as a known pair.
Do the ratio parts need to be whole numbers?
For simplifying, yes — the greatest-common-divisor method requires whole numbers. For solving a proportion, any numbers work.
Can a ratio part be zero?
Not for simplifying (a ratio needs two positive parts). For the proportion solver, A (the first term) must be non-zero, since it is divided by.
Is my data uploaded anywhere?
No. Calculation runs entirely in your browser.