Ratio Calculator

Simplify, scale, or fill in the missing part of a ratio.

Ratio Calculator

D (find)

Missing Value (D)

Simplifying a Ratio

Divide every part by their greatest common factor. 12:18 has a GCF of 6, so it reduces to 2:3. A simplified ratio says the same thing with smaller numbers, which makes two ratios far easier to compare.

Scaling Without Breaking It

Whatever you do to one part you do to all of them. Doubling a recipe written 2:3:5 gives 4:6:10, and the proportions are untouched. Adding two to each part instead gives 4:5:7, which is a completely different mixture and the most common ratio mistake there is.

Ratio Against Fraction

A ratio of 2:3 means five parts in total, so the first share is two fifths of the whole, not two thirds. Sharing 40 sweets in a 2:3 ratio gives 16 and 24. Reading a ratio as if it were a fraction is what produces the wrong split.

Finding a Missing Part

Equivalent ratios cross-multiply. If 3:4 equals 9:x, then 3x is 36 and x is 12. That single step handles scale drawings, map distances and unit pricing, which are the same question wearing different clothes.

Common Questions

How do I share an amount in a given ratio?

Add the parts to get the total number of shares, divide the amount by that total, then multiply by each part. For 40 in 2:3, one share is 8, giving 16 and 24.

Is 2:3 the same as two thirds?

No. 2:3 means two parts out of five in total, which is two fifths of the whole.

Can a ratio have three parts?

Yes. Simplify and scale it exactly the same way, applying every operation to all parts at once.