Rule of Three — Online Calculator

A is to B as C is to X. Fast, free and secure.

IS ABOUT TO
AS WELL AS
IS ABOUT TO

Benefits of UtiliApp

  • ✓100% free
  • ✓Works in the browser
  • ✓Not registered
  • ✓Deleted files

How to use

  1. 1.

    Fill in the values

    Enter A, B and C (empty values become 0).

  2. 2.

    'See the result'

    X is calculated automatically: (B × C) ÷ A.

  3. 3.

    Adjust if necessary

    Change the fields and the X updates instantly.

Frequently Asked Questions

Is the calculation proportional?

Yes, it's the direct simple rule of three: X = (B × C) ÷ A.

Is my data being sent?

No. The calculation occurs on the server without storing personal data.

Your files are processed locally and deleted.

The rule of three is used to find a proportional value when three values are known. It is common in discounts, conversions, and simple proportional variations.

Formula

Let A be to B as C is to X, then X = (B × C) ÷ A, provided that A is not equal to zero.

Tips

Keep the units consistent and check if the relationship is direct. For inverse relationships, adapt the formula.

See also