Cernarus

Convert Kilometers to Miles – Length Converter

This converter transforms a distance value in kilometres (km) to miles (mi) using the internationally established conversion relationship between the metre-based SI kilometre and the international mile.

The tool uses the defined constants used in metrology: one kilometre equals 1000 metres, and one international mile equals exactly 1609.344 metres. Results are presented numerically; choose display precision depending on your use case.

For regulatory, legal, or safety-critical uses consult the cited standards and apply required rounding, calibration, and measurement-traceability practices described by national and international metrology authorities.

Updated Nov 1, 2025

Interactive Converter

Convert between kilometer and mile with precision rounding.

Quick reference table

KilometerMile
1 km0.6214 mi
5 km3.1069 mi
10 km6.2137 mi
25 km15.5343 mi
50 km31.0686 mi
100 km62.1371 mi

Methodology

The converter applies a fixed, exact relationship derived from the metre definitions: 1 international mile = 1609.344 m and 1 kilometre = 1000 m. The conversion therefore uses exact derived factors.

For display the tool multiplies or divides by the exact conversion factors. Any rounding shown is for presentation only and does not change the underlying exact value used for calculations.

Accuracy guidance follows international metrology practice: present only as many significant digits as justified by the input measurement accuracy and the intended use. See citations for NIST, BIPM, and ISO references on units and measurement practice.

Worked examples

Example 1: Convert 5 km to miles. 5 × 0.6213711922373339 = 3.1068559611866695 → display as 3.106856 mi when rounded to 6 decimal places.

Example 2: Convert 0.1 km to miles. 0.1 × 0.6213711922373339 = 0.06213711922373339 → display as 0.0621371 mi when rounded to 7 significant digits.

Key takeaways

Use the exact conversion factors for calculation and apply rounding only for presentation.

For measurement traceability, follow guidance in the cited metrology standards and your local legal metrology rules when reporting distances for regulatory or contractual purposes.

Further resources

Expert Q&A

Which definition of 'mile' does this converter use?

This converter uses the international statute mile, defined as exactly 1609.344 metres (the common international standard agreed in 1959). It does not use the nautical mile or historical local miles.

Why do results sometimes differ from other tools?

Differences come from display rounding, the number of digits used for the conversion factor, or use of alternate unit definitions. This tool uses the exact metre-based definitions and only rounds for display.

How many decimal places should I trust?

Trust only as many digits as are supported by the original measurement's accuracy. For example, if a measured distance is accurate to the nearest metre, do not claim more significant digits in the converted value than justified. For formal use follow the rounding rules in relevant standards.

Can I convert negative values?

Yes. Mathematically the conversion applies to any real number, including negative values. For practical contexts negative distances typically indicate direction and should be treated according to your domain rules.

Is this suitable for legal or contractual measurements?

This tool provides numeric conversions based on internationally agreed definitions. For legal or regulatory measurements, confirm required procedures with the appropriate legal metrology authority and follow traceability, calibration, and rounding rules required by that authority.

What about 'nautical miles' and other mile types?

A nautical mile is different (exactly 1852 metres) and is not used here. Select a specialist converter if you need nautical miles or historical local mile units.

Sources & citations