Length Conversion Calculator
Convert length across eleven metric, international imperial, land-mile, and nautical-mile units.
Content updated August 6, 2026
International foot and mile factors are used. Historical U.S. survey-foot data can differ slightly and should be handled with its original geodetic definition.
Convert one nonnegative length between eleven metric and international units, then compare the same input across the full supported unit table. Common engineering, construction, road-distance, and nautical units are kept distinct.
Every conversion passes through metres using exact SI prefixes and internationally defined factors. The tool uses the international foot and mile, not the historical U.S. survey-foot definition.
The Length Conversion formula
Converted length = entered length × metres per source unit ÷ metres per destination unitSI prefixes and the supported international inch, foot, yard, mile, and nautical-mile factors are treated as exact definitions.
Worked example
One international mile multiplied by 1,609.344 metres per mile and divided by 1,000 metres per kilometre equals exactly 1.609344 kilometres.
Assumptions, rounding, and limitations
Assumptions
- The input is a nonnegative scalar length.
- Foot, yard, and land mile use international definitions.
- Nautical mile means the international nautical mile.
- Metric prefixes use powers of ten.
Rounding: The engine does not intentionally round intermediate results. Displays use up to 12 significant digits and scientific notation for values at least 1e12 or below 1e-7.
Limitations
- Does not convert historical U.S. survey feet, chains, rods, typographic points, astronomical units, or coordinate reference systems.
- Floating-point representation can introduce tiny binary approximations even when the published unit relationship is exact.
Sources
- Handbook 133 (2026), Appendix E: General Tables of Units of Measurement — National Institute of Standards and Technology
- NIST Guide to the SI, Appendix B: Conversion Factors — National Institute of Standards and Technology
International length definitions make conversion reproducible
NIST lists one international foot as exactly 0.3048 metre, one inch as exactly 2.54 centimetres, one yard as exactly 0.9144 metre, and one international mile as exactly 1.609344 kilometres.
The international nautical mile is exactly 1,852 metres. It remains a separate choice because a nautical mile and a land mile are not interchangeable.
Historical survey data needs its original unit basis
The U.S. survey foot was historically defined differently from the international foot. NIST says survey-foot definitions should generally be avoided after 2022 except for historic and legacy applications.
If coordinates, plats, or archived geodetic measurements specify U.S. survey feet, preserve that definition in the source workflow rather than silently converting them as international feet.
Frequently asked questions
▶How many kilometres are in one mile?
One international mile is exactly 1.609344 kilometres.
▶How many metres are in one foot?
One international foot is exactly 0.3048 metre.
▶Is a nautical mile the same as a land mile?
No. An international nautical mile is 1,852 metres, while an international land mile is 1,609.344 metres.
▶Does this use U.S. survey feet?
No. The foot and mile choices use international definitions. Historical survey-foot data needs a survey-specific conversion.
▶Why does the table sometimes use scientific notation?
Very large or very small converted values use scientific notation so significant digits remain visible without long runs of zeros.
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Open calculator →Disclaimer: Length Conversion Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.