Free Online Length Converter

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Length converter for every common metric and imperial unit — micrometers, millimeters, centimeters, meters, kilometers, inches, feet, yards, statute miles and nautical miles. Type a value on either side, pick the units, and the result updates instantly with full control over decimal precision.

Supported units: Micrometer (μm), Millimeter (mm), Centimeter (cm), Meter (m), Kilometer (km), Inch (in), Foot (ft), Yard (yd), Mile (mi), Nautical mile (nmi).

Centimeter (cm) → Inch (in)

Quick reference table

Centimeter (cm)Inch (in)
1 cm0.3937 inch
2 cm0.7874 inch
5 cm1.9685 inch
10 cm3.937 inch
25 cm9.8425 inch
50 cm19.685 inch
100 cm39.3701 inch

How length conversion works

Every length unit on this page is mapped to one canonical SI base — the meter. To convert from unit A to unit B the converter multiplies the input value by the meter-factor of A and divides by the meter-factor of B. The factors come from the international 1959 yard-and-pound agreement (1 inch = 25.4 mm exactly, 1 yard = 0.9144 m exactly, 1 statute mile = 1,609.344 m exactly) and ISO/SI definitions for the metric units (1 km = 1,000 m, 1 cm = 0.01 m). One nautical mile is exactly 1,852 m by international convention (BIPM, IHO). All arithmetic happens in JavaScript double-precision floats, which gives at least 15 significant decimal digits — far more than any tape measure or surveying instrument can resolve.

Metric vs imperial — a short history

The meter was first defined by the French Academy of Sciences in 1795 as one ten-millionth of the distance from the equator to the North Pole. Since 1983 it has been defined in terms of the speed of light. The imperial system, codified in 1824 in the United Kingdom and refined in the US Customary system, derived its inch and yard from medieval English standards; both were redefined in metric terms by the international yard-and-pound agreement of 1959 to remove the historical drift between national versions. Today the United States and a few other countries still use feet, yards and miles for everyday distances, while every other country and every scientific discipline uses the metric system. Converters like this one bridge the two systems with exact factors so engineering drawings, e-commerce shipping dimensions and travel plans round-trip without ambiguity.

Glossary

Micrometer (μm)

A micrometer, also called a micron, is one millionth of a meter (1 μm = 0.001 mm = 0.000039 inch). Used to measure cell sizes, semiconductor process nodes, paper thickness and aerosol particles such as PM2.5. The SI symbol uses the lowercase Greek letter mu, often written "um" in plain ASCII text.

Millimeter (mm)

A millimeter is one thousandth of a meter (1 mm = 0.1 cm = 0.03937 inch). It is the default fine-resolution unit on rulers, mechanical drawings, electronics PCBs and rainfall gauges. Ten millimeters make a centimeter; one inch contains exactly 25.4 millimeters by international agreement since 1959.

Centimeter (cm)

A centimeter is one hundredth of a meter (1 cm = 10 mm = 0.3937 inch). It is the everyday metric unit for clothing sizes, body measurements, paper formats and small object dimensions. Two and a half centimeters approximate one inch; ninety-one centimeters approximate one yard.

Meter (m)

The meter is the SI base unit of length, defined since 1983 as the distance light travels in vacuum in 1/299,792,458 of a second. One meter equals 100 cm, 1000 mm, 3.2808 ft or 1.0936 yd. It anchors all other metric length units and is the backbone of scientific and engineering measurement worldwide.

Kilometer (km)

A kilometer is one thousand meters (1 km = 0.6214 mile = 0.5400 nautical mile). It is the standard road-distance unit everywhere except the United States, the United Kingdom and a handful of other countries. Marathon distances, highway speeds and geographic distances on most maps use kilometers.

Inch (in)

An inch is the base small unit of the imperial and US customary systems, defined as exactly 25.4 mm since 1959. It appears on screen sizes, tire diameters, pipe fittings, lumber dimensions and DIY tape measures. Twelve inches make one foot; thirty-six make one yard.

Foot (ft)

A foot is twelve inches, defined as exactly 0.3048 m. It is the dominant length unit in US construction, aviation altitude, ceiling heights and human height in many English-speaking countries. Three feet make one yard; 5,280 feet make one statute mile.

Yard (yd)

A yard is three feet or 0.9144 m. It is used in American football fields, fabric and carpet sales, gardening hose lengths and golf course distances. The yard is close to one meter (1 yd = 0.9144 m) but not equal — a fact that matters for sports records and engineering drawings.

Mile (mi)

A statute mile is 5,280 feet or exactly 1,609.344 m. It is the road-distance unit in the United States, the United Kingdom and a few other countries; speed limits there are posted in miles per hour. Do not confuse with the nautical mile, which is longer and based on Earth's arc.

Nautical mile (nmi)

A nautical mile is exactly 1,852 m and equals one minute of arc along a meridian, which makes it the natural unit for marine and aviation navigation. One knot is one nautical mile per hour. A nautical mile is about 15% longer than a statute mile (1 nmi = 1.1508 mi).

Related tools

Centimeters to Inches
Convert centimeters to inches — exact factor 1 cm = 0.3937 in
Inches to Centimeters
Convert inches to centimeters — 1 inch = 2.54 cm exactly
Millimeters to Inches
Convert millimeters to inches — 1 mm = 0.03937 in (1 in = 25.4 mm)
Meters to Feet
Convert meters to feet — 1 m = 3.2808 ft (1 ft = 0.3048 m exactly)
Kilometers to Miles
Convert kilometers to miles — 1 km = 0.6214 mi (1 mi = 1.6093 km)
Feet to Meters
Convert feet to meters — exact factor 1 ft = 0.3048 m
Miles to Kilometers
Convert miles to kilometers — exact factor 1 mi = 1.609344 km