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Ratio Calculator

Solve ratios, find a missing value, and simplify a ratio to its lowest terms.

Examples

Choose which value is unknown (?) and fill in the rest of the proportion a : b = c : d.

a
:
b
=
c
:
d

How to use it

  • Proportion: enter three values in the proportion a:b = c:d, mark which one is unknown, and press "Calculate" to solve it by cross-multiplication.
  • Simplify ratio: enter a ratio such as 12:18:24 and get it in its simplest form.
  • Share by ratio: enter a total amount and a ratio (e.g. 2:3:5) to split it fairly between the parts.

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✍️ Written by the MathsUK teamChecked against the National Curriculum and GCSE specifications