Proportion calculator
Solve a direct or inverse proportion with three values and review the formula applied.
Processed on this device. The files are not sent to a server.
How to use this tool
- Select a direct or inverse relationship.
- Enter A, B and C; the result is X.
- Check the formula, copy or download the result.
What you should know
Inputs up to ±1 billion; output up to ±1,000 billion and display of 12 significant figures. Direct X = B × C / A; inverse X = A × B / C. Rejects zero divisor. It only works if the magnitudes maintain the chosen proportionality.
When do I use direct or inverse?
Direct when both magnitudes grow in the same proportion; for example quantity and price with a fixed rate. Inverse when its product is constant; for example people and time under equal conditions.