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Proportion Calculator

Enter any three values in a proportion and leave one box blank to solve the missing value instantly.

x = 203/5 = 12/x
60 = 60Cross products
0.6Common ratio

How to use this Proportion Calculator

Solve proportions in the form a/b = c/d with one unknown value. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.