How to use this calculator
Solve one missing value in a proportion equation using cross multiplication.
How the calculation works
- Enter three known values and leave one field blank.
- The calculator solves the missing value.
- The equation is shown with the solved result.
Formula
For a / b = c / x, x = (b x c) / a.
Example
If 2/5 = 6/x, then x = 15.
Understanding your result
Use the output as a practical starting point, then review it before using it in an important workflow.
Assumptions and limitations
- Leave exactly one field blank.
- Zero values can make some proportions undefined.
Frequently asked questions
Does this require an account?
No. The core tool works without creating a Tool2Do account.
Is my input included in share links or analytics?
No. Tool2Do share actions use the tool page URL and safe metadata, not private values or uploaded files.