Simplify a ratio
Enter two or three numbers. The third is optional.
Solve a proportion
Find the missing value X in A : B = C : X.
Divide an amount in a ratio
Split a total between two or three people or parts.
What is a ratio and how do you calculate it?
A ratio compares two or more quantities. A ratio of 2 : 3 means that for every 2 units of the first quantity there are 3 units of the second. Ratios are used in cooking, maps, finance, mixing and sharing.
Simplifying a ratio
To simplify a ratio, divide every term by their greatest common factor (GCF).
Solving a proportion
A proportion says two ratios are equal. If A : B = C : X, you find X by cross-multiplying.
For example, if 3 pens cost ₹12, then 5 pens cost (12 × 5) ÷ 3 = ₹20.
Dividing an amount in a ratio
Add the parts of the ratio, divide the total by that sum, then multiply by each part.
For example, to split ₹12,000 in the ratio 2 : 3, the sum of parts is 5. The shares are 12,000 × 2 ÷ 5 = ₹4,800 and 12,000 × 3 ÷ 5 = ₹7,200.
Where ratios are used
- Scaling recipes up or down.
- Sharing profit or expenses between partners.
- Reading map scales and model sizes.
- Mixing paint, concrete or fertiliser in the right proportions.
- Comparing financial figures such as debt to income.