Simplify two-part or three-part ratios, create equivalent ratios and divide a total in a chosen proportion.
All ratio parts are divided or multiplied by the same amount, so their proportion stays unchanged.
How to use the Ratio Calculator
Enter two values, or add a third value for a three-part ratio. The calculator converts decimals to whole-number parts where possible and divides every part by their highest common factor. Add a total amount if you also want to share that total in the same proportion.
How ratios are simplified
A ratio is in simplest form when its parts have no common factor greater than one. For example, 12:18 becomes 2:3 because both values are divided by 6.
| Calculation | Method |
|---|---|
| Simplify a ratio | Divide every part by the highest common factor |
| Create an equivalent ratio | Multiply or divide every part by the same number |
| Share a total | Divide the total by all ratio parts, then multiply by each part |
The BBC’s simplifying ratios guide also explains why dividing each side by the same highest common factor preserves the proportion.
Sharing an amount in a ratio
For a ratio of 2:3, there are five total parts. Sharing £100 means each part is worth £20, so the two shares are £40 and £60. The same method works for quantities, distances, ingredients and other units.
Decimals and zero values
Decimal ratios are scaled to whole numbers before simplification. A zero may be used in one part, but the ratio cannot contain only zeros because that would not define a meaningful proportion.
Related calculations
Use the Date Calculator for calendar intervals. Business ratios can support calculations in the Profit Margin Calculator. For dimensions and capacity, try the Volume Calculator. More tools are available on the United Kingdom Calculator homepage.
Frequently asked questions
Can the calculator simplify decimal ratios?
Yes. It first scales the decimal values into whole-number parts and then applies the highest common factor.
Can I calculate a three-part ratio?
Yes. Enter the optional third value and all three values will be simplified together.
What is an equivalent ratio?
It is a ratio with the same proportion, created by multiplying or dividing every part by the same non-zero number.
How do I divide money in a ratio?
Enter the ratio values and the total amount. The calculator displays the proportional share for each part.
Does the order of a ratio matter?
Yes. A ratio of 2:3 compares the first quantity with the second in that order, so reversing it changes the meaning.