Ratio Calculator guide
Ratio Calculator: Simplify, Scale and Share
Use our ratio calculator to simplify ratios, find a missing value in a proportion and share an amount in a given ratio.
By the AllCalculator editorial teamUpdated 16 October 20261 min read
Ratios compare amounts, like 2 parts squash to 3 parts water. Our Ratio Calculator simplifies them, solves proportions and shares amounts.
How to use the calculator (Ratio Calculator)
Choose what to do:
- Simplify a ratio: type it like 16:24 or 2:3:5.
- Find the missing value: solve A:B = C:?.
- Share an amount: split an amount in a ratio.
How it works
- Simplify: divide every part by the greatest common factor.
- Missing value: ? = B × C ÷ A.
- Share: add the parts, divide the amount by the total, then multiply by each part.
Worked examples
- With the calculator's default settings, 16:24 simplifies to 2:3 (dividing by 8).
- 3:4 = 15:? gives 20, since everything is multiplied by 5.
- Sharing £1,000 in the ratio 2:3:5 gives £200, £300 and £500.
Frequently asked questions
Can I use decimals?
Yes. 1.5:2.25 simplifies to 2:3.
How do I write a ratio as 1:n?
Divide both parts by the first. 2:3 is 1:1.5.
What's the difference between a ratio and a fraction?
A ratio compares parts to each other. A fraction compares a part to the whole. In 2:3, the first part is 2/5 of the total.
To simplify fractions, use our Fraction Calculator.
Sources and further reading
- GOV.UK: National curriculum in England – mathematicsgov.uk
- Wolfram MathWorld: Ratiomathworld.wolfram.com
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.