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Length Converter
Need to convert 5 feet 11 inches to centimeters before buying furniture from a European store, or figure out how many kilometers are in a 26.2-mile marathon? A length converter eliminates manual math and gives you the answer in seconds, whether you are switching between metric and imperial units or converting within the same system.
How Does a Length Converter Work?
A length converter uses fixed conversion factors to translate one unit of distance into another. Every unit pair has a defined ratio. For example, 1 inch equals exactly 2.54 centimeters, so converting 10 inches to centimeters requires a single multiplication: 10 × 2.54 = 25.4 cm.
The converter above accepts a numeric value, lets you select the source and target units, and applies the correct factor instantly. It covers over 50 units – from nanometers to astronomical units – so you do not need to memorize any formulas.
Common Units of Length
Metric system
The metric system is used by virtually every country for scientific, medical, and most everyday measurements. Units scale by powers of ten:
| Unit | Symbol | Equivalent in meters |
|---|---|---|
| Nanometer | nm | 0.000000001 |
| Micrometer | μm | 0.000001 |
| Millimeter | mm | 0.001 |
| Centimeter | cm | 0.01 |
| Meter | m | 1 |
| Kilometer | km | 1,000 |
Imperial and US customary system
The imperial system remains dominant in the United States, and partially in the United Kingdom and Canada for everyday use:
| Unit | Symbol | Equivalent in meters |
|---|---|---|
| Inch | in | 0.0254 |
| Foot | ft | 0.3048 |
| Yard | yd | 0.9144 |
| Mile | mi | 1,609.344 |
| Nautical mile | nmi | 1,852 |
Key Length Conversion Factors
These are the most frequently used conversions between metric and imperial units:
- 1 inch = 2.54 cm – the foundational factor for all inch-based conversions
- 1 foot = 30.48 cm (or 0.3048 m)
- 1 yard = 0.9144 m
- 1 mile = 1.60934 km
- 1 meter = 3.28084 feet
- 1 meter = 39.3701 inches
- 1 kilometer = 0.621371 miles
To convert in the opposite direction, divide instead of multiply. For instance, to convert 100 meters to feet: 100 × 3.28084 = 328.084 feet.
Length Conversion Table
Quick reference for the most common everyday conversions:
| Metric | Imperial | Imperial | Metric |
|---|---|---|---|
| 1 cm | 0.3937 in | 1 in | 2.54 cm |
| 1 m | 3.2808 ft | 1 ft | 0.3048 m |
| 1 m | 1.0936 yd | 1 yd | 0.9144 m |
| 1 km | 0.6214 mi | 1 mi | 1.6093 km |
How to Convert Feet and Inches to Centimeters
Height measurements in the US and UK typically use feet and inches. To convert to centimeters:
- Multiply the feet value by 30.48
- Multiply the inches value by 2.54
- Add the two results
Example: 5 ft 8 in → (5 × 30.48) + (8 × 2.54) = 152.40 + 20.32 = 172.72 cm
This is one of the most searched conversions online, driven by international travel, clothing sizes, and medical records that use different measurement systems depending on the country.
Metric vs. Imperial: Why Two Systems Exist
The metric system originated in France during the 1790s and was designed around the meter – originally defined as one ten-millionth of the distance from the equator to the North Pole. Its base-ten structure makes unit conversions straightforward.
The imperial system evolved from older English units, where a foot was literally based on the length of a human foot and an inch was the width of a thumb. In 1959, English-speaking nations agreed on standardized definitions (1 inch = 2.54 cm exactly) to eliminate discrepancies between the US, UK, Canadian, Australian, and New Zealand inch.
Today, only three countries have not officially adopted the metric system: the United States, Myanmar, and Liberia. Even in the US, science, medicine, and the military use metric units, while construction, road signs, and consumer goods still display imperial measurements.
Real-World Uses of Length Conversion
- Travel: Road signs in Europe show distances in kilometers; US drivers need miles
- Construction: Building plans may use millimeters while on-site workers read feet and inches
- E-commerce: Product dimensions listed in inches for US shoppers and centimeters for the rest of the world
- Sports: A marathon is 26.2 miles or 42.195 kilometers; a swimming pool is 25 yards or 25 meters depending on the country
- Aviation and maritime: Nautical miles are the standard unit; 1 nautical mile = 1.852 km = 1.15078 statute miles
This article is for general informational purposes. For engineering or scientific calculations, verify conversion factors against the current standards published by the relevant national metrology institute.
Frequently Asked Questions
How many centimeters are in one inch?
One inch equals exactly 2.54 centimeters. This conversion factor was internationally agreed upon in 1959 and is used in all standard length calculations between the imperial and metric systems.
What is the difference between a mile and a nautical mile?
A statute mile equals 1.609 kilometers, while a nautical mile equals exactly 1.852 kilometers. Nautical miles are used in aviation and maritime navigation because they correspond to one minute of latitude.
How do I convert feet and inches to centimeters?
Multiply the number of feet by 30.48, multiply the remaining inches by 2.54, then add both results. For example, 5 ft 9 in = (5 × 30.48) + (9 × 2.54) = 175.26 cm.
Why does the US use feet and inches instead of meters?
The United States legally adopted the metric system in 1866 but never mandated its exclusive use. Everyday life, construction, and road signs still rely on imperial units, making conversions between systems a daily necessity for international work.
How many millimeters are in one meter?
There are exactly 1,000 millimeters in one meter. The metric system uses powers of ten, so converting within it only requires moving the decimal point.
What is the smallest unit of length?
The smallest named unit in standard use is the yoctometer (1 × 10⁻²⁴ m). In practical measurement, the nanometer (1 × 10⁻⁹ m) is the smallest commonly used unit, applied in semiconductor manufacturing and molecular biology.