Length Converter
Convert between length units including meters, feet, inches, miles, kilometers, yards, and more. Free online converter.
What is Length Converter?
A length converter translates measurements between metric (millimeters, centimeters, meters, kilometers) and imperial (inches, feet, yards, miles) systems, plus specialized units like nautical miles. With most of the world using metric and the US primarily using imperial, conversion is a constant need in international business, engineering, construction, and everyday life. This tool handles all common conversions with precision appropriate to each unit.
How It Works
Enter a value and select the source and target units. The tool converts through a common base unit (meters), applying precise conversion factors: 1 inch = 0.0254 meters, 1 foot = 0.3048 meters, 1 mile = 1609.344 meters, etc. Results display with appropriate decimal precision based on the magnitude of the converted value. The tool handles very small (micrometer) to very large (astronomical unit) measurements correctly.
Quick Reference
| Metric | Imperial | Conversion |
|---|---|---|
| 1 cm | 0.394 inches | 1 inch = 2.54 cm |
| 1 meter | 3.281 feet | 1 foot = 0.3048 m |
| 1 km | 0.621 miles | 1 mile = 1.609 km |
| 30 cm | 11.81 inches | 1 foot = 12 inches |
| 100 m | 109.36 yards | 1 yard = 0.9144 m |
Common Use Cases
- •Converting architectural measurements between metric and imperial for international projects
- •Translating product dimensions from international suppliers using different measurement systems
- •Converting running distances between miles and kilometers for fitness tracking
- •Translating engineering specifications between metric and imperial systems
- •Converting map distances and travel measurements for trip planning
- •Translating fabric, lumber, and material measurements for DIY projects and construction
Frequently Asked Questions
How accurate are the conversions?▼
Conversions use standard conversion factors and display up to 8 significant digits.
What are the exact conversion factors between metric and imperial?▼
They are defined, not approximate: one inch is exactly 25.4 millimetres, one foot is exactly 0.3048 metres, one yard is exactly 0.9144 metres and one mile is exactly 1,609.344 metres. These have been the international definitions since the 1959 agreement.
Is a US mile the same as a UK mile?▼
Yes, both are 1,609.344 metres. The confusion usually comes from the nautical mile, which is different at 1,852 metres, being defined as one minute of latitude. It is used in aviation and at sea, and is the basis of the knot.
What is the difference between a US survey foot and an international foot?▼
The survey foot is longer by two parts per million, defined as 1200/3937 metres rather than 0.3048. Over a short distance it is irrelevant; across a state-wide survey it amounts to a difference of several centimetres. The US officially retired the survey foot at the end of 2022.
How many significant figures should I keep?▼
Match the precision of your input, since a conversion cannot create accuracy that was not there. Reporting a measurement of "about 5 feet" as 1.524 metres implies millimetre precision you do not have. Round to a sensible number of figures for the context.
How do light years and astronomical units relate to metres?▼
A light year is the distance light travels in a Julian year, roughly 9.461 × 10¹⁵ metres. An astronomical unit, the average Earth–Sun distance, is defined as exactly 149,597,870,700 metres. Both are units of distance, not time, despite how "light year" sounds.
Further Reading
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