How length conversion works
Every unit is first related to the meter, the SI base unit of length. CalcOS stores exact rational definitions where the standards define them exactly, then converts from the source unit to meters and from meters to the destination unit.
This canonical route prevents pairs such as miles-to-kilometers and feet-to-centimeters from drifting apart through separately rounded constants.
Common exact length relationships
| Unit | Exact relationship | Typical use |
|---|---|---|
| inch | 0.0254 meter | screens, dimensions, fabrication |
| foot | 0.3048 meter | height and construction |
| yard | 0.9144 meter | landscaping and textiles |
| mile | 1609.344 meters | road distance |
| kilometer | 1000 meters | metric travel distance |
Precision and rounding
Keep extra digits during the calculation and round only the displayed result. For construction, science, or manufacturing, choose precision that matches the original measurement; additional decimals do not make an imprecise input more accurate.
International foot versus survey foot
CalcOS uses the international foot, exactly 0.3048 meter. The former U.S. survey foot was retired for most U.S. federal surveying uses at the end of 2022. Historical survey data can require its legacy definition and should not be silently treated as international feet.
Authoritative references: BIPM SI Brochure and NIST Handbook 44, Appendix C.