How to Use Reverse Calculator
Choose the relationship that produced the result, such as x plus a known value, x multiplied by a known value, or result is x percent of a known value. Then enter the known result and the other known number. The calculator shows the unknown input and the substitution used.
Formula & Theory - Reverse Calculator
Each mode rearranges a different one-unknown equation:
add: x = result - known
subtract: x = result + known
multiply: x = result / known
divide: x = result × known
percent: x = result / known × 100The calculator is intentionally explicit about the selected equation. For example, x - known = result and known - x = result are different problems; this tool uses the first form shown in the menu. Multiplication and percent modes require the known value to be nonzero because division by zero has no valid numeric result.
Use Cases for Reverse Calculator
- Back-solving quantities - Find the missing starting value after an operation result is known.
- Percent checks - Determine what percentage one known result represents of another value.
- Math teaching - Connect forward operations with inverse operations.
Use the substitution line to confirm that the selected operation matches the real relationship you are trying to reverse.