Length Converter
Convert between different units of length and distance. Choose your units below for an instant result.
Popular Length Conversions
About Length Conversions
The metric and imperial systems
The metric system — built around the metre — was introduced in France in the 1790s and is now the international standard for science, engineering, and trade. Most countries measure everyday distances in metres and kilometres. The imperial system, which uses inches, feet, yards, and miles, persists in the United States and is still used informally in the United Kingdom alongside metric units.
Practical everyday conversions
The most common length conversions involve switching between miles and kilometres (road distances), feet and metres (height and room dimensions), and inches and centimetres (screen sizes, clothing, and body measurements). A useful rule of thumb: 1 inch ≈ 2.54 cm, and 1 mile ≈ 1.609 km.
Scientific and precision measurement
At very small scales, scientists use millimetres, micrometres (µm, one millionth of a metre), nanometres (nm, used for wavelengths of light), and even picometres for atomic-scale distances. At very large scales, astronomers use kilometres, astronomical units (AU — the Earth–Sun distance), light-years, and parsecs.