Length Converter
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By Abdul HadiReviewed by Dr. Emily Watson, PhD (Metrology)Published: Updated:
References
- [1]Bureau International des Poids et Mesures (BIPM), The International System of Units (SI) - 9th Edition, 2019. https://www.bipm.org/en/publications/si-brochure
- [2]National Institute of Standards and Technology (NIST), NIST Guide for the Use of the International System of Units (SI), 2008. https://physics.nist.gov/cuu/pdf/sp811.pdf
- [3]International Organization for Standardization (ISO), ISO 80000-3: Quantities and Units - Part 3: Space and Time, 2019.
How to Use?
- 1
Enter the length value
Type the numeric value you want to convert into the Value field.
- 2
Select the source unit
Choose the unit of your input value from the unit dropdown: m, km, cm, mm, mi, yd, ft, or in.
- 3
Choose the display unit
Use the Display Result In dropdown to select which unit appears highlighted as the primary result.
- 4
Review the result
The result panel shows your value in the chosen display unit, with all other supported units listed as alternatives below.
- 5
Cross-check key conversions
Use the reference table to verify common factors: 1 m = 3.281 ft, 1 km = 0.621 mi, 1 in = 25.4 mm.
- 6
Explore related converters
Use the area, volume, or speed converters linked on this page for additional unit conversion needs.
Worked Examples
1Convert 1 mile to kilometres
Given Values
lengthValue:1
lengthValue_unit:mi
Results
m:1609.344
2Convert 10 feet to metres
Given Values
lengthValue:10
lengthValue_unit:ft
Results
m:3.048
3Convert 1 metre to inches
Given Values
lengthValue:1
lengthValue_unit:m
Results
m:1
4Convert 100 kilometres to miles
Given Values
lengthValue:100
lengthValue_unit:km
Results
m:100000
5Convert 5 feet 6 inches to centimetres
Given Values
lengthValue:1.6764
lengthValue_unit:m
Results
m:1.6764
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Frequently Asked Questions
Conversions are based on internationally accepted values defined by the International System of Units (SI). Results are displayed with up to six decimal places for metres and appropriate precision for all other units.
Yes, this converter supports all major metric units (m, km, cm, mm) and imperial units (mi, yd, ft, in) with exact conversion factors defined by international agreement since 1959.
One inch equals exactly 2.54 centimetres by international agreement, established in 1959 and reaffirmed by the International Yard and Pound Agreement.
A nautical mile (1,852 m) is based on the Earth's circumference and one minute of latitude. It is used in aviation and maritime navigation. A statute mile (1,609.344 m) is used on land in the United States and United Kingdom.
Different industries and regions evolved separate measurement systems. The metric system (SI) is the international standard for science and most commerce, while imperial units remain common in the United States, Canada, and the United Kingdom for many everyday applications.
This converter handles linear length only. For area conversion, including square metres to square feet, use our dedicated area converter. The conversion factor for area is the square of the linear factor: 1 m² = 10.764 ft².
Since 1959, the international yard has been defined as exactly 0.9144 metres. This means 1 foot = 0.3048 m and 1 inch = 2.54 cm exactly, by international agreement among English-speaking countries.
The United States, Liberia, and Myanmar are the only countries that have not officially adopted the metric system. However, imperial units remain in common use for many everyday purposes in the United Kingdom and Canada alongside metric measurements.
One inch equals exactly 25.4 millimetres. This is a direct consequence of the 1959 international agreement that defined 1 inch = 2.54 cm, which equals 25.4 mm exactly.
One metre is approximately 1.094 yards, and one yard is exactly 0.9144 metres. The metre is slightly longer: 1 m is about 3.37 inches longer than 1 yd. The difference matters in sports fields, fabric measurement, and construction layout.
Modern surveyors use electronic distance measurement (EDM) instruments and GPS to measure distances with accuracies of one part per million or better. Distances are recorded in metres for GIS databases or feet for US property records, requiring precise unit conversion between systems.
The 1983 definition ties the metre to the speed of light, a universal physical constant that does not change. This replaced the platinum-iridium bar standard, which could be damaged, distorted, or replicated inconsistently. The speed of light definition makes the metre reproducible anywhere in the universe with sufficient precision.
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