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- Simplifies any ratio A : B to its lowest terms, even with decimals.
- Solves proportions such as 3 : 4 = 9 : ? using cross-multiplication.
- Splits a total amount into parts in a given ratio.
- Shows the ratio as a fraction, a decimal, 1 : n form and percentages.
How to use the ratio calculator
Choose a mode
Pick simplify, solve a proportion, or split a total.
Enter A and B
These are the two terms of your ratio, such as 24 and 36.
Add the extra value
In solve mode enter C, the known term of the second ratio. In split mode enter the total amount.
Read the answer
The result appears with the full working, so you can copy the steps into homework or a report.
How ratios are calculated
Simplifying a ratio
A : B = (A ÷ GCD) : (B ÷ GCD)
GCD is the greatest common divisor of A and B. Decimal ratios are first multiplied by 10, 100 or 1,000 to make whole numbers.
Solving a proportion
A : B = C : x
x = B × C ÷ A
This is cross-multiplication: A × x = B × C.
Splitting a total
One part = total ÷ (A + B)
Share A = A × one part, Share B = B × one part
Example 1: simplify 24 : 36
The greatest common divisor of 24 and 36 is 12.
- 24 ÷ 12 2
- 36 ÷ 12 3
- Simplest form 2 : 3
A ratio with decimals works the same way: 1.5 : 2.25 becomes 150 : 225, which also simplifies to 2 : 3.
Example 2: solve 3 : 4 = 9 : ?
Cross-multiply and divide by A.
- 3 × x 4 × 9 = 36
- x 36 ÷ 3 = 12
- Answer 3 : 4 = 9 : 12
The scale factor is 9 ÷ 3 = 3, so both terms are tripled.
Example 3: split 500 in the ratio 2 : 3
There are 2 + 3 = 5 parts in total.
- One part 500 ÷ 5 = 100
- Share A 2 × 100 = 200
- Share B 3 × 100 = 300
The two shares add back up to 500, which is a quick way to check your work.
Where a ratio calculator helps
Recipes and mixing
Scale ingredients, concrete, paint or fertiliser mixes while keeping the same proportions.
Screens and images
Work out aspect ratios such as 16 : 9 and resize photos or videos without stretching.
Money and sharing
Split profits, bills or prize money between people in an agreed ratio.
Maps and models
Convert between scale drawings and real sizes with a simple proportion.
A ratio of 2 : 3 means the first part is 2/5 of the whole, or 40%. You can work with that fraction in the fraction calculator, turn it into a percent with the percentage calculator, or find the common factor yourself with the GCD calculator.
Ratio calculator FAQ
How do I simplify a ratio?
Divide both terms by their greatest common divisor. For 24 : 36 the GCD is 12, so the ratio becomes 2 : 3.
Can I simplify a ratio with decimals?
Yes. The calculator multiplies both terms by a power of 10 to remove the decimals and then simplifies, so 1.5 : 2.25 becomes 2 : 3.
How do I solve a missing value in a proportion?
Use cross-multiplication. For A : B = C : x, the missing value is x = B × C ÷ A.
How do I divide an amount in a ratio?
Add the ratio terms to get the number of parts, divide the total by that number, and multiply by each term.
What does 1 : n form mean?
It rewrites the ratio so the first term is 1. For example 2 : 3 becomes 1 : 1.5, which is handy for comparing ratios.
Is a ratio the same as a fraction?
They are related but not the same. The ratio 2 : 3 compares two parts, while the fraction 2/3 compares a part with a whole. In a 2 : 3 split, the first part is 2/5 of the total.