Rule of three calculator
Solve a direct proportion from three values.
Rule of three calculator
Your result appears here
Adjust the values to see your result automatically.
Sida loo isticmaalo Rule of three calculator
The Rule of three calculator takes three known values A, B and C and returns the missing fourth value D. In direct proportion it solves A / B = C / D, giving D = B × C / A. In inverse proportion it solves A × B = C × D, giving D = A × B / C. The formula with your numbers is shown with the result.
- Adjust the values; an initial result is calculated from the defaults.
- Change the basic settings or open Advanced mode to fine-tune the result.
- Review and copy or download your result. Pause Live results to run manually. Sources or individual settings above 20,000 characters require an explicit run.
Waxa qalabkani taageero
Solve a direct proportion from three values.
- A
- Set this value for your task.
- B
- Set this value for your task.
- C
- Set this value for your task.
- Proportion
- Direct · Inverse
Xadka iyo habaynta
Use finite numbers, valid dates and the ranges shown by each control. Invalid values produce an error without a downloadable result.
Su’aalaha badanaa la isweydiiyo
How do I solve a rule of three problem?
Enter the known pair as A and B and the new value as C, then pick Direct. If 5 items cost 10, then 15 items cost D = 10 × 15 / 5 = 30. The result also displays the formula with your numbers filled in.
When should I use inverse proportion?
Use Inverse when one quantity goes down as the other goes up, such as workers and days to finish a job. The calculator keeps A × B equal to C × D, so 5 workers taking 10 days means 15 workers take 5 × 10 / 15 days.
Why does the calculator say A must be greater than zero?
A is a divisor in the direct formula, so it must be greater than zero in both modes. In inverse mode, C is the divisor and must also be greater than zero. B can be any finite number.
Where is my input processed?
This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.
What are the input limits?
Use finite numbers, valid dates and the ranges shown by each control. Invalid values produce an error without a downloadable result.