Ratio Calculator
Simplify any ratio to its lowest terms and see it as a decimal.
How to use the Ratio Calculator
- Enter the first number.
- Enter the second number.
- See the ratio reduced to its lowest whole-number terms.
Divide both sides by their greatest common divisor (GCD)
About the Ratio Calculator
Enter two numbers and this calculator reduces the ratio to its lowest whole-number terms, then shows it as a decimal and as a percentage. The simplification is done by dividing both sides by their greatest common divisor, found with Euclid’s algorithm: 16:9 is already lowest because the GCD of 16 and 9 is 1, while 16:8 divides by 8 down to 2:1.
That is the whole trick, and it is the same operation as reducing a fraction — a ratio and a fraction are the same object written differently, which is why 16:8, 16/8 and 2 are three views of one number. Ratios are what you want when the parts matter as parts: mixing concrete, scaling a recipe from four people to six, setting an aspect ratio, or splitting a bill by shares. A decimal loses that structure; “2:1” tells you to use two scoops for every one, while “2.0” does not.
The calculator simplifies only when both inputs are whole numbers, because decimals have no meaningful GCD — enter 1.5:2 and you still get the decimal and percentage views, but not a reduced whole-number pair. Multiply both sides until they are integers first (1.5:2 becomes 3:4) and it will simplify. To find the divisor directly, see the GCD and LCM calculator; to express one part of a whole, the percentage calculator.
Frequently asked questions
What does simplifying a ratio actually do?
It divides both sides by their greatest common divisor. 16:8 has a GCD of 8, so it reduces to 2:1. The proportion is unchanged — only the numbers get smaller.
Why won’t it simplify my decimals?
The greatest common divisor is only defined for whole numbers. Scale both sides up until they are integers — 1.5:2 becomes 3:4 if you double both — and it will reduce.
What is the difference between a ratio and a fraction?
Mostly notation. 2:1 and 2/1 carry the same information, and both simplify the same way. Ratios are preferred when you are thinking in parts, such as mixing or scaling.
How do I scale a recipe with a ratio?
Keep the simplified ratio fixed and multiply both sides by the same factor. A 2:1 rice-to-water ratio stays 2:1 whether you are cooking one cup or ten.
What does the percentage row mean?
It is the first number divided by the second, expressed as a percentage. For 16:9 that is 177.78%, meaning the first quantity is a bit over one and three quarter times the second.
Guides & articles about this tool
How to Simplify Ratios Easily (Free Ratio Calculator)
Stuck with a ratio? Use our free simplify ratio calculator—it reduces any ratio to its lowest terms and gives the decimal in one click. This guide explain…