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Length Converter

Convert cm, mm, m, km, inches, feet, yards & miles

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Type the distance you want to convert into the length value field.
  2. 2.Choose the source unit under 'From' and the target unit under 'To' — for example centimeters to inches.
  3. 3.Read the converted result instantly, or tick 'Show all units at once' to see millimeters through nautical miles together.

About Length Converter

A length converter changes any distance between metric and imperial units — millimeters (mm), centimeters (cm), meters (m), kilometers (km), inches (in), feet (ft), yards (yd), miles (mi), nautical miles (nmi), and micrometers (μm) — instantly and entirely in your browser, with nothing uploaded. Every unit is defined as an exact number of meters, so the tool converts by routing through the meter as a single common base: it multiplies your value by the meters-per-unit of the source, then divides by the meters-per-unit of the target. That one-hop-through-meters approach is why any pair works, including mixed metric-to-imperial conversions like cm to inches.

The metric (SI) side is built on powers of ten around the meter: 1 cm = 0.01 m, 1 mm = 0.001 m, 1 km = 1000 m, and 1 μm (micrometer) = 0.000001 m. That decimal structure is what makes metric arithmetic easy — every step is just a shift of the decimal point, so converting mm to cm to m to km never needs a lookup table.

The imperial and US customary side is anchored to the meter by exact international definitions, not approximations. Since the 1959 international yard and pound agreement, 1 inch is defined as exactly 0.0254 meters. Everything else follows in closed form: 1 foot = 12 inches = 0.3048 m, 1 yard = 3 feet = 36 inches = 0.9144 m, and 1 mile = 5280 feet = 1609.344 m. Because these are exact definitions, the everyday conversions are exact too: 1 inch = 2.54 cm, and 1 cm is about 0.393701 inches.

The nautical mile is the odd one out. It is not tied to feet at all — the international nautical mile is defined as exactly 1852 meters, a value adopted in Monaco in 1929 and used in aviation and marine navigation because it corresponds to roughly one minute of latitude along a meridian. That is why a nautical mile (1852 m) is noticeably longer than a statute land mile (1609.344 m).

To use the converter, type a value, choose your source and target units, and read the result immediately — there is no button to press. Enable 'Show all units at once' to see the same length expressed across every unit from micrometers to nautical miles in a single table, which is handy for spec sheets that mix systems. When you cross many orders of magnitude, such as micrometers to kilometers, the result switches to scientific notation so precision is preserved.

The factors here follow NIST SP 811 (the NIST Guide to the SI) and NIST Handbook 44, so the inch stays at exactly 0.0254 m and the nautical mile at exactly 1852 m with no rounding of the definitions. Everything runs client-side, so your values never leave your device.

Frequently asked questions

How many inches are in a centimeter?
One centimeter equals about 0.393701 inches, and one inch equals exactly 2.54 centimeters. The inch is defined as exactly 0.0254 meters, so these conversions are exact rather than rounded. To go from cm to inches, divide the number of centimeters by 2.54.
How do you convert cm to inches?
Divide the number of centimeters by 2.54, because 1 inch is defined as exactly 2.54 cm (0.0254 m). For example, 30 cm ÷ 2.54 is about 11.81 inches. This converter does it instantly — pick centimeters as the source unit and inches as the target and read the result.
Why is a nautical mile different from a regular mile?
A statute (land) mile is 1609.344 meters, defined from feet (5280 ft). A nautical mile is defined separately as exactly 1852 meters, based on roughly one minute of latitude, and is used in aviation and shipping. So a nautical mile is about 15% longer than a land mile.
Is 1 inch exactly 2.54 cm?
Yes. Since the 1959 international yard and pound agreement, 1 inch is defined as exactly 0.0254 meters, which is exactly 2.54 centimeters. It is a definition rather than a measurement, so there is no rounding error in the inch-to-centimeter relationship.
What is a micrometer (μm)?
A micrometer, also called a micron, is one millionth of a meter (0.000001 m) — one thousandth of a millimeter. It is used for very small distances such as cell sizes, wavelengths, and manufacturing tolerances. This tool includes μm so you can convert it against millimeters, inches, or even kilometers.

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