How to use the ratio calculator
Pick a mode. Simplify reduces A : B to its lowest terms and also shows it as a decimal, a fraction, a percent and in "1 : x" form. Split a total shares an amount in the ratio A : B — 500 split 3 : 2 gives 300 and 200. Compare tells you whether A : B and C : D are the same ratio. Decimals are fine in every mode: 0.5 : 0.25 simplifies to 2 : 1.
What a ratio is
A ratio compares two quantities by division. "3 : 2" means that for every 3 of the first thing there are 2 of the second — three parts to two parts. Order matters: a 3 : 2 ratio of adults to children is not the same as 2 : 3. Written 3 : 2, 3/2 or "3 to 2", it means the same thing.
Simplifying a ratio with the GCF
A ratio is in simplest form when its two terms share no common factor other than 1. To get there, divide both terms by their greatest common factor. For 12 : 18 the GCF is 6, so 12 ÷ 6 : 18 ÷ 6 = 2 : 3. If a term has decimals, first multiply both terms by 10, 100 or 1,000 until they are whole numbers: 0.5 : 0.25 becomes 50 : 25, and dividing by 25 gives 2 : 1. The GCF calculator shows the factor steps.
Splitting a total in a ratio
- Add the parts of the ratio: 3 + 2 = 5 parts.
- Divide the total by the number of parts to find the value of one part: 500 ÷ 5 = 100.
- Multiply each term by that value: 3 × 100 = 300 and 2 × 100 = 200.
The same three steps share money between partners, mix liquids in the right strength and scale recipes up or down.
Worked examples
Lemonade: a recipe uses lemon juice and water in the ratio 1 : 4. To make 2 liters (2,000 mL) there are 5 parts of 400 mL each, so you need 400 mL of juice and 1,600 mL of water.
Screen aspect ratio: a 1920 × 1080 display has a GCF of 120, so its shape is 1920 ÷ 120 : 1080 ÷ 120 = 16 : 9. In 1 : x form that is 1 : 0.5625 — the height is 56.25% of the width. A 1280 × 720 screen (GCF 80) is also 16 : 9, so both show the same picture without black bars.
Concrete: a common general-purpose mix is 1 : 2 : 3 by volume — cement : sand : gravel. Taken two at a time, sand to gravel is 2 : 3, so 750 kg of aggregate splits into 5 parts of 150 kg: 300 kg of sand and 450 kg of gravel. Cement to sand is 1 : 2, so those 300 kg of sand call for 150 kg of cement.
Ratio, fraction, rate and proportion
| Term | Compares | Example |
|---|---|---|
| Ratio | Two parts of the same kind | 3 cups flour : 2 cups sugar |
| Fraction | A part to the whole | flour is 3/5 of the dry mix |
| Rate | Two different units | 60 miles per hour |
| Proportion | Two equal ratios | 3 : 2 = 6 : 4 |
The fraction trap: a 3 : 2 ratio does not mean the first quantity is 3/2 of the whole. The first is 3/5 of the total and the second is 2/5. For a missing term in two equal ratios use the proportion calculator; to add or divide fractions, the fraction calculator.
Frequently asked questions
How do I simplify a ratio that has decimals?
Multiply both terms by the same power of 10 until both are whole numbers, then divide both by their greatest common factor. 1.5 : 2.5 becomes 15 : 25, and dividing by 5 gives 3 : 5.
Can a ratio be written as a percentage?
Yes. Divide the first term by the second and multiply by 100: 3 : 4 = 0.75 = 75%. If instead you want each part as a share of the total, divide by the sum of the parts: in a 3 : 4 ratio the first part is 3 of 7, or about 42.86%.
How do I split an amount in a given ratio?
Add the parts, divide the amount by that sum, then multiply by each term. $1,200 split 5 : 3 has 8 parts of $150, so the shares are $750 and $450.
Are 2 : 3 and 4 : 6 the same ratio?
Yes. Both simplify to 2 : 3, and the cross products agree: 2 × 6 = 12 and 3 × 4 = 12. Equivalent ratios describe the same relationship at a different scale.
What does 16 : 9 mean as a number?
16 ÷ 9 = 1.7778, so the width is about 1.78 times the height. Turned around, the height is 9 ÷ 16 = 0.5625 of the width.
Last updated: October 9, 2026