Length Converter
Enter a value to instantly convert between length units.
Length conversions are some of the most common calculations people need day to day — checking a room's dimensions in feet when furniture is sized in centimeters, converting a recipe's measurements, or figuring out how many miles a route in kilometers actually covers. Because the world uses two parallel systems (metric and imperial/US customary), almost everyone runs into a length conversion sooner or later, whether they're reading a tape measure, a map, or a product spec sheet.
1 Centimeter = 0.3937 Inch
Key Formulas
Centimeter → Inch
in = cm × 0.393701Kilometer → Mile
mi = km × 0.621371Foot → Meter
m = ft × 0.3048Inch → Centimeter
cm = in × 2.54Popular Conversions
Choose Any Length Units
Choose any two length units in the converter above. Dedicated conversion guides appear here only after their formulas and supporting content have been reviewed.
About Length Conversions
History & Background
The metric system's base unit, the meter, was originally defined in 1793 as one ten-millionth of the distance from the North Pole to the equator along a meridian through Paris — an attempt to create a unit derived from the natural world rather than a king's body part or a local custom. Imperial and US customary units, by contrast, trace back to older English units with origins in body measurements and agricultural practice: the foot to the length of a human foot, the yard to a stride, and the inch historically to the width of a thumb. Today, both systems are defined with mathematical precision relative to the meter — since 1959, the international inch has been defined as exactly 25.4 millimeters, which is the figure used in every length conversion on this site.
How to Use This Converter
Pick the unit you're converting from and the unit you want, enter your value, and the result updates instantly. For most everyday conversions — centimeters to inches, kilometers to miles, feet to meters — the default precision (a handful of decimal places) is more than enough. If you're working on something that requires extreme precision (engineering tolerances, scientific measurements), the formula shown on each conversion page gives you the exact factor used, sourced from NIST SP 811.
Frequently Asked Questions
Why isn't there a round number for converting inches to centimeters?
There used to be slightly different definitions of the inch in different countries before 1959, when an international agreement fixed the inch at exactly 25.4 mm. That number (2.54 cm = 1 inch) is now the universal standard, but because it's based on the metric system's millimeter rather than a round fraction, conversions in the other direction (cm to inches) produce a repeating decimal (1 cm = 0.3937... inches).
Which countries still use feet, inches, and miles?
The United States is the largest country that uses imperial/US customary units as its primary system for everyday measurements. The UK officially uses metric for most purposes but commonly uses miles for road distances and feet/inches for height and some other everyday contexts. Most other countries use the metric system exclusively.
What's the difference between a nautical mile and a regular mile?
A nautical mile (1,852 meters) is based on the distance covered by one minute of latitude on the Earth's surface, and is used in maritime and aviation navigation because it relates directly to map coordinates. A statute mile (1,609.344 meters), used for road distances, is a different and slightly shorter unit with origins in old Roman and English measurements.
Popular Use Cases
These conversions are also featured in: