Ratio Calculator
Simplify a ratio to its lowest whole-number terms, or solve a proportion to find a missing value when two ratios are equal. Handles decimal terms too. Calculates in your browser.
Simplified ratio
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Show the math
A ratio is simplified by dividing both terms by their greatest common divisor:
a : b → (a ÷ g) : (b ÷ g), where g = gcd(a, b)
A proportion keeps two ratios equal, so the missing term is:
a : b = c : x → x = b × c ÷ a
Decimal terms are scaled to whole numbers before simplifying, so 1.5 : 3 becomes 1 : 2.
What this does
A ratio calculator simplifies a ratio to its lowest whole-number terms, or solves a proportion to find a missing value when two ratios are equal. It handles decimal terms as well as whole numbers.
How to use it
- Enter the two terms of your ratio to simplify it.
- Or enter three terms of a proportion to solve for the fourth.
- Read the reduced ratio or the missing value.
How it works
Simplifying divides both terms by their greatest common divisor. Solving a proportion cross-multiplies: when a : b equals c : x, the missing value is b × c ÷ a. Decimal terms are scaled to whole numbers first.
a : b = c : x → x = b × c ÷ a
Understanding your result
A simplified ratio is the same proportion expressed in the smallest whole numbers, so 16:8 and 2:1 describe the identical relationship, only scaled, use the simplest form for mixing or comparing. When solving a proportion the missing value assumes the two ratios are genuinely equal; if your real quantities are not proportional, the answer will not hold. Decimal terms are scaled to whole numbers first, so expect a larger but equivalent ratio.
Example
16 : 8 reduces to 2 : 1, and 1.5 : 3 simplifies to 1 : 2. For the proportion 1 : 2 = 5 : x, the answer is x = 10.
Sources & methodology
Last updated .
Frequently asked questions
How is a ratio simplified?
Both terms are divided by their greatest common divisor. So 16 : 8 reduces to 2 : 1, and 4 : 8 reduces to 1 : 2.
Can it handle decimals?
Yes. Decimal terms are scaled up to whole numbers before reducing, so 1.5 : 3 simplifies to 1 : 2.
How does solving a proportion work?
A proportion sets two ratios equal: a : b = c : x. The missing value is x = b × c ÷ a. For 1 : 2 = 5 : x, the answer is 10.
Is my data stored?
No. Everything is calculated locally in your browser.
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