Online Ratio & Proportion Calculator

Quickly solve for the missing value in a proportion. Ideal for students, designers, and anyone needing to solve ratio problems.

Solve the Proportion
Enter three values to calculate the fourth. Leave the field you want to solve for empty.
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How to Use
  • The calculator is set up as A : B = C : D.
  • Enter any three known values into their respective fields.
  • Leave the field for the unknown value empty.
  • Click the "Calculate" button to find the missing value.
  • The result will automatically appear in the empty field.
Frequently Asked Questions