How to use the inverse proportion calculator
- Write the two products in the four boxes: a × b = c × d.
- Enter three numbers and leave the number you want to find empty.
- Select Calculate. The result shows the missing value, the completed equation, and the calculation.
Example
For 4 × 10 = 8 × ?, enter 4, 10, and 8. The missing value is 4 × 10 ÷ 8 = 5. The completed equation is 4 × 10 = 8 × 5. Both products equal 40. Any one of the four boxes can be left empty.
Input and limits
- Use ordinary decimals with a point and no units or separators.
- Exactly one box must be empty. Use Copy result for your notes; Clear removes inputs and results.
- A zero divisor either makes the equation impossible or leaves the answer undetermined. A zero answer is accepted when the other factor is nonzero.
- Displayed results use up to two decimal places; very small or large values use scientific notation. Internal calculations keep their precision.