Length Converter
How does length conversion work?
Length conversion is one of the most common unit conversions needed in everyday life. This converter supports all major metric and imperial length units. Key conversions to remember: 1 mile equals 1.609 km, 1 foot equals 30.48 cm, 1 inch equals 2.54 cm, and 1 meter equals 3.281 feet. Need to continue this calculation? Try the Area Converter or the Weight Converter.
Metric vs Imperial
The metric system (meters, kilometers) is used by most countries worldwide. The imperial system (feet, miles, inches) is primarily used in the United States, Liberia, and Myanmar. Scientists universally use metric measurements.
What should you check before converting units?
Conversions are simple, but accuracy depends on using the correct unit. Always check whether the value is metric, imperial, digital, or temperature-based before comparing results. For work, study, travel, recipes, or shopping, round only at the end so the final number stays more accurate. If a result will be used for safety, construction, medicine, or finance, confirm it with an official standard or professional source.
Who finds this calculator most useful?
This converter is useful for travel, recipes, study, product comparison, engineering notes, online shopping, and daily measurements. It is especially helpful when two sources use different systems, such as metric and imperial units.
How should you read and use the output?
The Length Converter is built for people who want a fast answer without losing context. It keeps the calculation simple, shows the result clearly, and helps you understand what the number means before you use it in a real decision.
Conversion tools help translate values between measurement systems quickly. They are especially useful when comparing products, recipes, travel details, technical values, or international information.
How many centimetres are in an inch, and metres in a mile?
Length is measured in two major systems worldwide: the metric system (used by most countries) and the imperial/US customary system (used primarily in the United States and, for some measurements, the United Kingdom). Converting between them requires knowing the exact conversion factors. Errors in unit conversion have caused real-world failures — most famously NASA's 1999 Mars Climate Orbiter crash, where a navigation error arose from mixing metric and imperial units.
Complete length conversion reference table
- 1 kilometre (km) = 1,000 metres = 0.621371 miles = 1,093.61 yards = 3,280.84 feet
- 1 metre (m) = 100 centimetres = 1,000 millimetres = 3.28084 feet = 39.3701 inches
- 1 centimetre (cm) = 10 millimetres = 0.393701 inches = 0.0328084 feet
- 1 mile = 1.60934 kilometres = 1,760 yards = 5,280 feet = 63,360 inches
- 1 yard = 3 feet = 36 inches = 0.9144 metres = 91.44 centimetres
- 1 foot = 12 inches = 30.48 centimetres = 0.3048 metres
- 1 inch = 2.54 centimetres = 25.4 millimetres = 0.0254 metres
- 1 nautical mile = 1.852 kilometres = 1.15078 miles (used in aviation and maritime navigation)
Most common everyday conversion scenarios
Height (person's height): global passports and official documents use centimetres. US measurements use feet and inches. 5 feet 9 inches = (5 × 30.48) + (9 × 2.54) = 152.4 + 22.86 = 175.26 cm.
Running distance: 5 km = 5 × 0.621371 = 3.107 miles. A marathon (42.195 km) = 26.219 miles.
Construction and home renovation: Room dimensions are often given in feet in older global properties and metres in newer ones. 12 feet = 12 × 30.48 = 365.76 cm = 3.66 metres.
Fabric purchasing: Cloth is often sold by the metre; some patterns specify yards. 1 yard = 0.9144 metres. 3 yards = 2.74 metres.
Screen sizes: TV and monitor screen sizes are given in inches (diagonal). A 55-inch TV: 55 × 2.54 = 139.7 cm screen diagonal.
global traditional units of length
India historically used a variety of traditional length measurements, some of which are still used in rural contexts or specific industries:
- Haat (Cubit): Approximately 45–47 cm — the distance from the elbow to the tip of the middle finger
- Gaj (Yard equivalent): Officially standardised to 0.9144 metres (same as the international yard)
- Kos: Approximately 2–3.2 km depending on the region — traditionally used for road distances
- Furlong: 201.168 metres (1/8 of a mile) — still used in horse racing
Astronomy and extreme length scales
- 1 astronomical unit (AU): 149,597,870.7 km — average distance from Earth to Sun
- 1 light-year: 9.461 × 10¹² km — distance light travels in one year
- 1 parsec: 3.086 × 10¹³ km = 3.26 light-years — used in galactic distance measurement
- 1 angstrom: 10⁻¹⁰ metres = 0.1 nanometres — used in atomic and molecular physics
Frequently asked questions about length conversion
How many centimetres are in a foot? Exactly 30.48 cm. This is an exact definition — 1 inch = 2.54 cm (exact), so 1 foot = 12 × 2.54 = 30.48 cm exactly.
What is the difference between a nautical mile and a regular mile? A statute (regular) mile = 1,609.34 metres. A nautical mile = 1,852 metres. Nautical miles are based on the circumference of the Earth (one nautical mile equals one minute of latitude). They are used in aviation and marine navigation because they correspond directly to navigation charts.
Why does the US still use imperial units? The US is one of three countries that have not officially adopted the metric system (along with Liberia and Myanmar). Historical inertia, the cost of conversion, and industry entrenchment have maintained imperial units in everyday use despite the US scientific community using metric exclusively.
Length unit conversion reference table
| Unit | Metres | Feet | Inches | Miles |
|---|---|---|---|---|
| 1 millimetre (mm) | 0.001 | 0.00328 | 0.03937 | — |
| 1 centimetre (cm) | 0.01 | 0.03281 | 0.3937 | — |
| 1 metre (m) | 1 | 3.28084 | 39.37 | 0.000621 |
| 1 kilometre (km) | 1,000 | 3,280.84 | 39,370 | 0.62137 |
| 1 inch (in) | 0.0254 | 0.08333 | 1 | — |
| 1 foot (ft) | 0.3048 | 1 | 12 | 0.000189 |
| 1 yard (yd) | 0.9144 | 3 | 36 | 0.000568 |
| 1 mile (mi) | 1,609.34 | 5,280 | 63,360 | 1 |
| 1 nautical mile | 1,852 | 6,076.1 | 72,913 | 1.15078 |
Common human heights in feet, inches, and centimetres
| Feet & Inches | Inches | Centimetres |
|---|---|---|
| 5'0" | 60" | 152.4 cm |
| 5'2" | 62" | 157.5 cm |
| 5'4" | 64" | 162.6 cm |
| 5'6" | 66" | 167.6 cm |
| 5'8" | 68" | 172.7 cm |
| 5'10" | 70" | 177.8 cm |
| 6'0" | 72" | 182.9 cm |
| 6'2" | 74" | 187.9 cm |
| 6'4" | 76" | 193.0 cm |
Sources & References
Sources: BIPM (Bureau International des Poids et Mesures) — The International System of Units (SI), 9th edition, 2019. Exact definition: 1 inch = 2.54 cm; 1 mile = 1,609.344 m.
Indian traditional length units: survey of regional systems
| Unit | Region | Metres | Common Use |
|---|---|---|---|
| Gaz / Yard | North India | 0.9144m | Fabric (cloth sold by the gaz) |
| Hath (cubit) | South Asia | ~0.457m | Traditional carpentry and masonry |
| Angul (finger-breadth) | Classical India | ~0.019m | Ancient measurement system |
| Kos / Krosh | North India | ~3.2 km | Road distance (pre-modern) |
| Yojana | Classical texts | ~12–15 km | Used in Vedic texts; approximate |
Body-based length measurements: origin of imperial units
Imperial units were originally derived from the human body — which is why they feel intuitive even though metric is more logical. Inch: originally the width of a human thumb (or three barleycorns). Foot: literally the length of a foot (King Henry I standardised it at 12 inches in 1324). Yard: the distance from King Henry I's nose to his outstretched thumb. Fathom: the span of two outstretched arms (still used in nautical depth: 1 fathom = 6 feet = 1.83m). Furlong: "furrow length" — the distance a team of oxen could plough without resting (one-eighth of a mile). These origins explain why the same system that measures height in feet uses miles for long distances — they evolved independently for different purposes. Related: Area Converter · Speed Converter.