How the unit converter works
The converter keeps length and mass in separate measurement families, preventing meaningless conversions such as metres to kilograms. Each conversion passes through a documented SI base unit for consistency.
Calculation method
Length values are converted to metres and mass values to kilograms before being converted to the requested unit. The international foot is exactly 0.3048 metres, and the pound value used is 0.45359237 kilograms.
Converted value = input value × source-unit factor ÷ destination-unit factor.Assumptions and counting rules
- The foot is the international foot, not the retired U.S. survey foot.
- Pounds represent avoirdupois pounds.
- Displayed results use up to ten decimal places; very small rounding differences can appear in repeated conversions.
Practical examples
5 kilometres to miles
5 × 1,000 ÷ 1,609.344 ≈ 3.106856 miles.
Useful for trip distances.
6 feet to metres
6 × 0.3048 = 1.8288 metres.
The international-foot factor is exact.
150 pounds to kilograms
150 × 0.45359237 ≈ 68.0388555 kilograms.
Useful for comparing measurement systems.
Common mistakes
- Mixing unit families, such as length and mass.
- Using a survey-foot factor for ordinary measurements.
- Rounding the conversion factor before completing the calculation.
- Confusing mass in pounds with pound-force.
Edge cases
- Negative values are accepted because they can represent positions or changes, although negative physical mass may not be meaningful.
- Zero converts to zero in every compatible unit.
- Large values may display using locale formatting and limited decimal precision.
Questions specific to this tool
Are the conversion factors exact?
The kilometre, metre, international foot, mile, gram, kilogram, and avoirdupois pound relationships used here are defined conversions; displayed rounding can still shorten the result.
Why can't I convert metres to pounds?
Metres measure length and pounds measure mass, so there is no direct conversion without additional physical information.
What is the difference between a foot and a U.S. survey foot?
They were slightly different. The tool uses the international foot, which is the appropriate factor for common modern conversions.
Last reviewed: August 3, 2026 · Method version 1.0.0