Converting a measurement means multiplying by an exact ratio and then reporting the result at a sensible precision. Most errors come from an inverted ratio, the wrong prefix, or rounding before the final step.
01Steps
Identify the quantity and the exact conversion factor.
Multiply or divide so the unit you are leaving cancels out.
Round only at the end, to the precision the input supports.
Check the direction: a smaller unit needs more of them.
02Limitations
Conversion factors are exact for defined SI and binary prefixes, but the measurement uncertainty of the input still limits the honest precision of the output.