📏 Length Converter

Convert length units instantly — meters, feet, inches, centimeters, kilometers, miles, and more. Supports 18 units across metric, imperial, nautical, and astronomical scales. Used by engineers, travellers, scientists, and students worldwide.

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1 in = 2.54 cm | 1 ft = 30.48 cm | 1 mi = 1.609 km = 5,280 ft

Common Length Conversions — Quick Reference

1 nautical mile = 1.852 km

ly → km

1 light year = 9.461×10¹² km

pc → km

1 parsec = 3.086×10¹³ km

Å → m

1 angstrom = 10⁻¹⁰ m

au → km

1 AU = 149,597,871 km

Frequently Asked Questions — Length Converter

A meter (m) is the base unit of length in the SI system. It is defined as the distance light travels in vacuum in exactly 1/299,792,458 of a second. All metric length units derive from the meter.

There are exactly 12 inches in one foot. 1 foot = 12 inches = 30.48 cm.

Divide cm by 2.54 to get inches. Example: 10 cm ÷ 2.54 = 3.937 inches. Reverse: multiply inches by 2.54. 1 inch = 2.54 cm exactly.

One mile = exactly 1.609344 km. One km = 0.621371 miles. Quick tip: km × 0.621 = miles; miles × 1.609 = km.

Length measures an object from end to end. Distance measures space between two points. Both use the same units and convert identically.

Metric (used by 95% of the world): mm, cm, m, km. Imperial/US: inch, foot, yard, mile. Science: meters; aviation: feet; maritime: nautical miles.

Multiply feet by 0.3048 to get meters. Example: 6 ft × 0.3048 = 1.8288 m. Reverse: m × 3.28084 = feet. Quick tip: 5 ft ≈ 1.524 m; 6 ft ≈ 1.829 m.

About Length Measurement

Length is one of the seven fundamental SI units and the basis of all distance, size, and spatial measurements. Two major systems are in use globally: the metric system (meters, centimeters, kilometers) used by 195 countries, and the imperial/US customary system (inches, feet, yards, miles) still used in the United States and partially in the UK. Converting between them is one of the most common everyday calculation needs — from reading international road signs to following foreign recipes, buying imported furniture, or understanding a person's height described in a different system.

The Metric System

The meter was defined during the French Revolution (1793) as one ten-millionth of the distance from the North Pole to the equator. Today it is defined by the speed of light — the most precise physical constant available. The metric system is used by 95% of the world's population.

Key metric units: nm → μm → mm → cm → dm → m → km. Each step is a factor of 10.

The Imperial System

Imperial units — inch, foot, yard, mile — evolved from medieval English measures. An inch was originally the width of a thumb; a foot was literally the length of a human foot. The US, UK (partially), and Myanmar still use imperial units.

Key Imperial chain: 12 in = 1 ft · 3 ft = 1 yd · 1,760 yd = 1 mi · 1 in = 2.54 cm exactly.

Who Uses the Length Converter?

🏗️ Construction & Engineering

Converting between metric and imperial for blueprints, CAD drawings, and international project specifications.

✈️ Aviation & Navigation

Aviation uses feet for altitude worldwide; nautical miles for distance. Pilots convert constantly between systems.

🔬 Science & Research

Scientists work in SI units (meters, nanometers, parsecs) and need to convert to imperial for US collaborators.

🏃 Sports & Fitness

Track events use meters (100m, 5000m); road races use miles and km. Athletes convert between systems for training.

🌍 International Travel

Travellers switching between countries that use km vs miles for road distances, cm vs inches for clothing sizes.

🏠 Home & DIY

Furniture dimensions, room measurements, and renovation work often mix metric and imperial from different countries.

Quick Mental Math for Length

km ↔ miles

Multiply km by 0.621 for miles. Rough shortcut: km × 0.6 ≈ miles. 100 km ≈ 62 mi.

cm ↔ inches

Divide cm by 2.54 for inches. Quick: cm ÷ 2.5 ≈ inches. 30 cm ≈ 12 in (1 foot).

meters ↔ feet

1 m ≈ 3.28 ft. Quick: m × 3 + 10% ≈ feet. 1.8 m ≈ 6 ft.

All Length Conversions

Common

km → mi mi → km m → ft ft → m cm → in in → cm m → cm ft → in

Metric

km → m m → km cm → m cm → mm mm → cm m → mm km → cm m → μm mm → μm μm → nm m → nm

Metric ↔ Imperial

m → yd yd → m mm → in in → mm km → ft m → in cm → ft ft → cm mi → m km → yd

Imperial

in → ft mi → ft ft → mi mi → yd yd → mi yd → ft ft → yd yd → in in → yd mi → in

Nautical

nmi → km km → nmi nmi → mi mi → nmi nmi → m nmi → ft fathom → m m → fathom

Survey & Land

chain → m m → chain fur → km fur → mi fur → m km → fur

Nano & Micro

nm → μm μm → mm nm → mm nm → cm Å → nm nm → Å Å → μm μm → m nm → m

Astronomical

ly → km ly → mi au → km au → mi parsec → ly km → au parsec → km ly → m

Common Length Conversions

1 inch= 2.54 cm

1 foot= 30.48 cm

1 mile= 1.609 km

1 meter= 3.281 ft

100 cm= 39.37 in

1 km= 0.621 mi

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Metric Prefixes Reference

Understanding metric prefixes helps you convert any metric length unit instantly.

Prefix	Symbol	Multiplier	Example
Tera	T	10¹²	1 Tm = 1 trillion meters
Giga	G	10⁹	1 Gm = 1 billion meters
Mega	M	10⁶	1 Mm = 1,000 km
Kilo	k	10³	1 km = 1,000 m
Hecto	h	10²	1 hm = 100 m
Deca	da	10¹	1 dam = 10 m
Base	—	10⁰	1 meter
Deci	d	10⁻¹	1 dm = 0.1 m
Centi	c	10⁻²	1 cm = 0.01 m
Milli	m	10⁻³	1 mm = 0.001 m
Micro	μ	10⁻⁶	1 μm = 0.000001 m
Nano	n	10⁻⁹	1 nm = 10⁻⁹ m