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Length Unit Converter

Convert length measurements between metric and imperial units - meters, centimeters, millimeters, kilometers, feet, inches, yards and miles.

Inputs

Result

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These calculators provide estimates and educational results. Always verify critical engineering calculations against applicable standards and qualified professional review.

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What Is It

Length conversion is the most common unit conversion in engineering work spanning metric and imperial systems - a single project often mixes millimeter-specified components with foot-and-inch site dimensions, making quick, accurate conversion essential.

How to Calculate

Enter a value, select the unit you're converting from, and the unit you want to convert to. The result updates using exact conversion factors (for example, 1 inch = 25.4mm exactly).

Example

Converting 10 feet to meters: 10 × 0.3048 = 3.048 meters. Converting 500mm to inches: 500 / 25.4, about 19.69 inches.

Recommendations

For precise engineering work, always use exact conversion factors (as this tool does) rather than rounded approximations like '1 inch is about 2.5cm' - small rounding errors compound significantly across a large drawing or long cable run.

Frequently Asked Questions

Is 1 inch exactly 25.4mm?

Yes - since 1959, the international inch has been defined as exactly 25.4 millimeters, making this and all derived length conversions exact rather than approximate.

Why do some countries use feet and inches while others use meters?

It's a matter of historical standards adoption - the US retains imperial units for most everyday and construction measurement, while most of the world, along with the scientific and engineering community globally, uses the metric system.

Which unit should I use for engineering drawings?

Follow the convention of the project's governing standard or client - millimeters are standard for mechanical and structural drawings in metric countries, while the US construction industry typically still specifies feet and inches.

Last reviewed: 2026-09-12