Decision tools built for clarity
Length Converter
Convert values between supported length units.
Enter a length value, then choose its source unit and target unit.
Methodology
Formula or transformation
Normalizes the submitted length to meters, then applies the target-unit conversion factor.
Variables
- Submitted length
- Source unit factor in meters
- Canonical length in meters
- Target unit factor in meters
- Converted length
Units
- Millimeter
- Centimeter
- Meter
- Kilometer
- Inch
- Foot
- Yard
- Mile
Rounding policy
The converted length is rounded to the declared result scale using half away from zero.
The converter maps the source unit to metres and then maps metres to the requested target unit using fixed SI conversion factors.
Convert values between supported length units.
Reviewed sources
- NIST — SI conversion factors Reviewed on 2026-09-04
Formula review history
-
Initial formula and source review.
Reviewed 2026-09-04 for formula version nist-length-conversion-v1
Assumptions
- The input is a length, not an area or volume.
- Unit labels use their standard SI or internationally defined meanings.
Limitations
- Displayed rounding can hide digits from the converted value.
- The conversion does not account for measurement uncertainty or instrument precision.
Worked example
Using the exact international conversion, 1 mile = 1,609.344 metres = 1.609344 kilometres.
Frequently asked questions
Is a mile exactly 1.609344 kilometres?
Yes, for the internationally defined statute mile used by this converter.
Does conversion increase accuracy?
No. Changing units cannot improve the original measurement quality.