Conversion Calculator
Length Converter
Convert between metric and imperial length units including millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles.
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The guide, formula, examples, and FAQ are available below.
How to Use This Calculator
Enter Value
Type your value into the input field. For example: e.g., 100. Minimum value: 0.
Select From
Choose the appropriate option from the "From" dropdown. Options include: Millimeters (mm), Centimeters (cm), Meters (m), Kilometers (km), Inches (in), Feet (ft), Yards (yd), Miles (mi).
Select To
Choose the appropriate option from the "To" dropdown. Options include: Millimeters (mm), Centimeters (cm), Meters (m), Kilometers (km), Inches (in), Feet (ft), Yards (yd), Miles (mi).
View Your Result
The result appears beside the calculator with the main answer and a detailed calculation breakdown.
Adjust and Explore
Change any input value and calculate again. Use the copy and share controls to save or send your result.
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Unit conversion note
Conversion calculators use standard metric, imperial, and US customary relationships.
Cooking and regional units may vary, so check the unit system shown on the calculator before relying on a result.
Source and review references
Last reviewed by the Calculator Trust Editorial Team. To report an issue, email contact [at] calculatortrust.com.
Common Examples
Understanding the Concept
Length conversion is one of the most frequently needed unit conversions in everyday life, construction, engineering, and science. The world uses two primary systems of measurement: the metric system (millimeters, centimeters, meters, kilometers) used by most countries, and the imperial system (inches, feet, yards, miles) still widely used in the United States, United Kingdom, and a few other nations. This converter makes it easy to switch between any of these units instantly.
Metric System Units
The metric system is a decimal-based system where each unit is related by powers of 10:
- Millimeter (mm): One thousandth of a meter. Used for precise measurements like the thickness of a credit card (~0.76 mm).
- Centimeter (cm): One hundredth of a meter. Common in everyday measurements like height and clothing sizes in metric countries.
- Meter (m): The base unit of length in the metric system. Roughly the distance from the floor to a doorknob.
- Kilometer (km): One thousand meters. Used for measuring distances between cities and for road signs in most countries.
Imperial System Units
The imperial system uses units with non-decimal relationships:
- Inch (in): The smallest commonly used imperial unit. One inch equals 2.54 centimeters. Used for screen sizes, hardware, and everyday small measurements.
- Foot (ft): Equal to 12 inches or 30.48 centimeters. Commonly used for measuring height and room dimensions in the U.S.
- Yard (yd): Equal to 3 feet or 0.9144 meters. Used in sports (football fields) and fabric measurement.
- Mile (mi): Equal to 5,280 feet or 1,609.344 meters. Used for road distances and speed limits in the U.S. and U.K.
Key Conversion Factors
The most important conversion factors to remember are:
- 1 inch = 2.54 cm (exact definition)
- 1 foot = 30.48 cm
- 1 yard = 0.9144 m
- 1 mile = 1.609344 km
- 1 meter = 3.28084 feet
- 1 km = 0.621371 miles
The inch-to-centimeter conversion (1 in = 2.54 cm) is the foundational link between the two systems. All other imperial-to-metric conversions are derived from this exact definition.
Frequently Asked Questions
How many feet are in a meter?
How many kilometers are in a mile?
Why does the U.S. use the imperial system?
How do I convert between metric units?
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Written and reviewed by Calculator Trust Editorial Team
Our calculators are built using verified formulas from academic, government, and scientific sources. Content is fact-checked and reviewed for accuracy.