Ratio Calculator
Work with ratios in two ways. Simplify a ratio to its smallest whole numbers, or split an amount, like money or ingredients, in a given ratio.
Simplified ratio
2 : 3
Check the highlighted fields to see your result.
- For each 1 of A
- 1 : 1.5
- Share of the total
- 40.0% / 60.0%
Results are estimates for information only and do not constitute financial, medical, or legal advice.
How ratios work
A ratio A : B says how many parts of one thing there are for each part of another. To simplify it, divide both numbers by their greatest common divisor. To split an amount, divide it into A + B equal parts and give A of them to the first and B to the second.
The formulas
A : B = (A ÷ gcd) : (B ÷ gcd)
Part A = total × A ÷ (A + B)
Worked example
- Simplify 12 : 18. The greatest common divisor is 6, so 12 : 18 = 2 : 3.
- Split 120 in the ratio 2 : 3. There are 2 + 3 = 5 parts, and each part is 120 ÷ 5 = 24.
- So the first gets 2 × 24 = 48 and the second gets 3 × 24 = 72.
Frequently asked questions
What does a ratio like 2 : 3 mean?
It compares two amounts: for every 2 parts of the first, there are 3 parts of the second. Together they make 5 parts, so the first is 2/5 (40%) of the total and the second is 3/5 (60%).
Can I simplify a ratio with decimals?
Yes. The calculator turns the decimals into whole numbers before simplifying, so 0.5 : 1.25 becomes 2 : 5.
How do I use a ratio for a recipe or a mix?
Choose "Split an amount in a ratio," enter the parts of the ratio and the total amount. For example, 750 ml of a drink mixed 1 : 4 is 150 ml of concentrate and 600 ml of water.