Proportion calculator
Find an unknown value in a direct or inverse proportion.
How to use
- Choose Direct when quantities grow by the same factor, or Inverse when one increases as the other decreases proportionally.
- Fill A and B with a known pair. In C, enter the new value for A's quantity; the calculation will find the corresponding value of X for B's quantity.
- Click Calculate and review X and the formula. Before interpreting the result, check that A and C use the same unit.
How it works
The calculation only applies when the quantities have a constant proportional relationship and compatible units.
An example
For a direct proportion, if 3 notebooks cost $24, 5 cost $40. For an inverse proportion, if 2 machines finish a job in 6 hours, 4 equivalent machines take 3 hours.
Common questions
How do I distinguish a direct proportion from an inverse one?
In a direct proportion, multiplying one quantity by a factor multiplies the other by that factor. In an inverse proportion, the other quantity is divided by that factor.
Can I mix hours and minutes in one calculation?
Convert values of the same quantity to the same unit first. For example, 2 hours equal 120 minutes.