A measurement has two parts: a number and a unit. Change the unit correctly and the number changes with it, while the physical amount stays the same.
Core idea
A conversion factor is a statement of equality
If 1 metre equals 3.28084 feet, then both expressions describe the same length. That equality becomes a factor you can multiply by.
value× conversion factor=new value
Three steps
Set up a clean conversion
- 01Identify the starting and target units
Write down what you have and what the answer must use.
- 02Choose the correct relationship
Use an established factor and check which direction it runs.
- 03Calculate, label and round
Keep the unit beside the answer and round only at the end.
Avoid these
Common conversion mistakes
Reversing the factor
Multiplying when the conversion requires division.
Rounding too early
Losing accuracy before the final step.
Mixing unit systems
Combining values before converting them to compatible units.