Quick answer
Length conversion multiplies by the ratio of unit factors to metres. 1 mile equals exactly 1.609344 kilometres.
Enter a value, choose the units and decimals. The calculator returns the converted length.
Related tools: Feet and Inches Calculator: Add or subtract two lengths given in feet and inches. Scale Conversion Calculator: Convert between model and actual lengths at a 1:N scale. SAE to Metric Converter: Fractional or decimal inches to millimeters.
How to use the Length Converter
- Enter value.
- Choose from: Millimetre (mm), Centimetre (cm), Metre (m), Kilometre (km), Micrometre (µm) and Nanometre (nm) and 9 more.
- Choose to: Millimetre (mm), Centimetre (cm), Metre (m), Kilometre (km), Micrometre (µm) and Nanometre (nm) and 9 more.
- Enter decimal places (between 0 and 10). It starts at 4.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Value | A number | — |
| From | Choose one: Millimetre (mm); Centimetre (cm); Metre (m); Kilometre (km); Micrometre (µm); Nanometre (nm); Inch (in); Foot (ft); … | Starts at Millimetre (mm) |
| To | Choose one: Millimetre (mm); Centimetre (cm); Metre (m); Kilometre (km); Micrometre (µm); Nanometre (nm); Inch (in); Foot (ft); … | Starts at Centimetre (cm) |
| Decimal places | A number | ≥ 0, ≤ 10, starts at 4 |
Formula and method
Formula
result = value × (factor of source ÷ factor of target), base unit: metre
IEEE-754 double precision; displayed to the chosen number of decimal places (default 4). Very small or large results are shown in scientific notation.
Every unit is defined by an exact or published factor to the base unit (metre). The value is multiplied by the source factor and divided by the target factor.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Value = 1; From = Mile (mi); To = Kilometre (km); Decimal places = 6.
| Result | Value |
|---|---|
| Mile (mi) → Kilometre (km) | 1.609344 |
| Input | 1 Mile (mi) |
Example 2
Inputs: Value = 12; From = Inch (in); To = Foot (ft); Decimal places = 4.
| Result | Value |
|---|---|
| Inch (in) → Foot (ft) | 1 |
| Input | 12 Inch (in) |
Example 3
Inputs: Value = 1; From = Nautical mile (nmi); To = Metre (m); Decimal places = 2.
| Result | Value |
|---|---|
| Nautical mile (nmi) → Metre (m) | 1,852 |
| Input | 1 Nautical mile (nmi) |
The first line is the headline result (mile (mi) → Kilometre (km)). Below it the length Converter lists input, which describe the same case from other angles. IEEE-754 double precision; displayed to the chosen number of decimal places (default 4). Very small or large results are shown in scientific notation.
Unit reference
Each unit expressed in the base unit used for the calculation. Conversions go through this base unit, so any unit can be converted to any other in the table.
| Unit | Equals (in metre) |
|---|---|
| Millimetre (mm) | 0.001 |
| Centimetre (cm) | 0.01 |
| Metre (m) | 1 |
| Kilometre (km) | 1000 |
| Micrometre (µm) | 0.000001 |
| Nanometre (nm) | 1e-9 |
| Inch (in) | 0.0254 |
| Foot (ft) | 0.3048 |
| Yard (yd) | 0.9144 |
| Mile (mi) | 1609.344 |
| Nautical mile (nmi) | 1852 |
| Mil (thou) | 0.0000254 |
| Fathom | 1.8288 |
| Furlong | 201.168 |
| Light-year | 9460730473000000 |
Exact definitions
Since 1959 the inch is exactly 25.4 mm, the foot 0.3048 m and the mile 1.609344 km. 1 yard = 0.9144 m and 1 nautical mile = 1.852 km.
Searches such as 'steps to miles' depend on your stride length, not a fixed factor. This page converts exact length units; to turn steps into distance use the Steps to Distance Calculator.
Quick checks
To convert miles to kilometres, multiply by 1.6; to convert kilometres to miles, multiply by 0.62. A marathon is 42.195 km or 26.2 miles.
How the result changes with value
Holding every other input at the first worked example, this table changes only value. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Value | Mile (mi) → Kilometre (km) | Input |
|---|---|---|
| 0.5 | 0.804672 | 0.5 Mile (mi) |
| 1 | 1.609344 | 1 Mile (mi) |
| 2 | 3.218688 | 2 Mile (mi) |
| 4 | 6.437376 | 4 Mile (mi) |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Value: left empty shows "Enter value." beside that field and no result.
Choosing between the Length Converter and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Feet and Inches Calculator](/converters/feet-inches-calculator/) | first length: feet, first length: inches and second length: feet | Result |
| [Scale Conversion Calculator](/converters/scale-conversion/) | scale denominator N, convert and length | Converted length |
| [SAE to Metric Converter](/converters/sae-to-metric-calculator/) | size in inches | Millimeters |
| [Chord Length Calculator](/math/chord-length/) | radius and central angle | Chord length |
| [Gutter Length Calculator](/construction/gutter-length-calculator/) | length of each eave and section length | Total gutter length |
Background: unit conversion
Many customary units are defined exactly in terms of metric ones: since the 1959 International Yard and Pound Agreement an inch is exactly 2.54 cm and a pound is exactly 0.45359237 kg (NIST SP 811 lists these). So most length and mass conversions are exact apart from the rounding of the displayed result.
To convert, multiply the value by the source unit's factor to reach the base unit, then divide by the target unit's factor; the unit table on this page lists every factor used. Temperature and fuel economy are the exceptions, because they are not simple multiples.
Assumptions and limitations
- Negative values are allowed
- Zero converts to zero (except L/100 km, where zero is invalid)
- Units from different quantities cannot be converted
- Very large or tiny results switch to exponent notation
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for value to confirm this.
Frequently asked questions
How many feet in a mile?
There are 5,280 feet in a mile, so 1 mile converts to 5,280 ft in the length converter.
How many cm in an inch?
One inch is exactly 2.54 centimetres, so 10 inches is 25.4 cm.
What is a nautical mile?
1,852 metres, based on a minute of latitude.
What does the Length Converter calculate?
Convert between metric and imperial lengths. It returns Mile (mi) → Kilometre (km) and Input.
What formula does the Length Converter use?
result = value × (factor of source ÷ factor of target), base unit: metre. Every unit is defined by an exact or published factor to the base unit (metre).
What is an example of a length result?
With value 1, from Mile (mi), to Kilometre (km) and decimal places 6, the mile (mi) → Kilometre (km) is 1.609344.
Where does the method come from?
The method follows: NIST SP 811 (2008), Appendix B.8: international yard = 0.9144 m exactly; BIPM SI Brochure (9th ed.).
Related calculators
- Feet and Inches Calculator — Add or subtract two lengths given in feet and inches.
- Scale Conversion Calculator — Convert between model and actual lengths at a 1:N scale.
- SAE to Metric Converter — Fractional or decimal inches to millimeters.
- Chord Length Calculator — Length of a chord from the radius and central angle.
- Arc Length Calculator — Length of a circular arc.
Sources
- NIST SP 811 (2008), Appendix B.8: international yard = 0.9144 m exactly
- BIPM SI Brochure (9th ed.)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.