Calculators tool

Ratio Calculator

Solve A:B = C:D, simplify and scale ratios.

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Solve A : B = C : D

Fill in any three boxes and leave one empty.

:=:

Simplify a ratio

–Simplest form
–As 1 : n
–Share of total

Scale a ratio

About this tool

Ratio Calculator solves proportions, reduces ratios to their simplest form and scales them. Use it to resize images, scale recipes, mix concrete or paint, or split money or costs in a set proportion.

How to use Ratio Calculator

  1. Fill in three of the four boxes to solve a proportion.
  2. Type a ratio to simplify it.
  3. Scale a ratio or split a total in that ratio.

Questions people ask

How do I solve A:B = C:D for the missing value?

Cross-multiply: A × D = B × C. So D = B × C ÷ A. For 3:4 = 15:D, D = 4 × 15 ÷ 3 = 20.

How do I simplify a ratio?

Divide every part by the greatest common divisor. 1920:1080 has a GCD of 120, giving 16:9. Decimals are first scaled to whole numbers, so 1.5:2 becomes 15:20 and then 3:4.

How do I split an amount in a ratio?

Add the parts, then share the total in proportion. To split 250 in 2:3, the parts total 5, so the shares are 250 × 2/5 = 100 and 250 × 3/5 = 150.

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