Unit conversion is reliable when you identify the source unit, target unit and conversion factor before doing the arithmetic.
Length and area
Length conversion uses one factor. Area conversion uses the square of the length factor, so a square metre is not converted with the same number as one metre.
Mass, speed and volume
Keep the numerator and denominator units together. For speed, convert distance and time separately or use a factor that already includes both units.
Avoid common mistakes
Write the units beside every intermediate value. Check whether the answer should be linear, square, cubic or per-time, then compare it with a rough mental estimate.
- Check the direction of the conversion factor.
- Do not mix metric and imperial inputs without converting.
- Label the final answer with its unit.
Frequently asked questions
Why can area conversion look unexpectedly large?
Area has two dimensions, so the length conversion factor is applied twice. Volume applies it three times.