Length converter

1 cm ≈ 0.39370079 in

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About length conversions

Convert distances and heights between metric and US/imperial units. The inch has been defined as exactly 2.54 cm since 1959, so every length factor here is exact.

Common length conversions

Length units explained

Unit	System	Definition and notes
Metre (m)	SI (metric)	Base unitThe SI base unit of length. Since 1983 it has been defined by the speed of light, which travels exactly 299,792,458 m in one second.
Kilometre (km)	SI (metric)	1 km = 1,000 m (exact)Defined as exactly 1,000 metres.
Centimetre (cm)	SI (metric)	1 cm = 0.01 m (exact)Defined as exactly 1/100 of a metre.
Millimetre (mm)	SI (metric)	1 mm = 0.001 m (exact)Defined as exactly 1/1,000 of a metre.
Micrometre (µm)	SI (metric)	1 µm = 0.000001 m (exact)
Nanometre (nm)	SI (metric)	1 nm = 1 × 10⁻⁹ m (exact)
Inch (in)	US & imperial (identical)	1 in = 0.0254 m (exact)The international inch, defined as exactly 2.54 cm since 1959.
Foot (ft)	US & imperial (identical)	1 ft = 0.3048 m (exact)The international foot: 12 inches, defined as exactly 0.3048 m since 1959.
Yard (yd)	US & imperial (identical)	1 yd = 0.9144 m (exact)Defined as exactly 3 feet = 0.9144 m.
Mile (mi)	US & imperial (identical)	1 mi = 1,609.344 m (exact)The international mile: 5,280 feet, or exactly 1,609.344 m.
Nautical mile (nmi)	other	1 nmi = 1,852 m (exact)The nautical mile used at sea and in the air: exactly 1,852 m.
Mil (thou) (mil)	US & imperial (identical)	1 mil = 0.0000254 m (exact)A thousandth of an inch (also called a thou): exactly 25.4 µm.
US survey foot (ft (US survey))	US customary	1 ft (US survey) ≈ 0.30480061 mThe US survey foot, exactly 1200/3937 m. It was retired at the end of 2022 but still turns up in older land surveys.
Astronomical unit (au)	other	1 au = 149,597,870,700 m (exact)The average distance from Earth to the Sun, fixed at exactly 149,597,870,700 m in 2012.
Light-year (ly)	other	1 ly ≈ 9.4607305 × 10¹⁵ mThe distance light travels in one year: exactly 9,460,730,472,580,800 m, as set by the International Astronomical Union.
Ångström (Å)	other	1 Å = 1 × 10⁻¹⁰ m (exact)

Centimetres to inches conversion table

centimetre (cm) to inch (in)
Centimetres (cm)	Inches (in)
0.1 cm	0.03937 in
0.5 cm	0.19685 in
1 cm	0.3937 in
2 cm	0.7874 in
3 cm	1.1811 in
4 cm	1.5748 in
5 cm	1.9685 in
6 cm	2.3622 in
7 cm	2.7559 in
8 cm	3.1496 in
9 cm	3.5433 in
10 cm	3.937 in
15 cm	5.9055 in
20 cm	7.874 in
25 cm	9.8425 in
30 cm	11.811 in
40 cm	15.748 in
50 cm	19.685 in
75 cm	29.528 in
100 cm	39.37 in
250 cm	98.425 in
500 cm	196.85 in
1,000 cm	393.7 in

Frequently asked questions

Which length units can I convert?

metres (m), kilometres (km), centimetres (cm), millimetres (mm), micrometres (µm), nanometres (nm), inches (in), feet (ft), yards (yd), miles (mi), nautical miles (nmi), mils (mil), US survey feet (ft (US survey)), astronomical units (au), light-years (ly), ångströms (Å).

How accurate are the results?

Every unit is stored with its exact defining factor (NIST SP 811, NIST Handbook 44 or the BIPM SI Brochure). Calculations use double-precision arithmetic and are rounded only for display, to 5 significant figures by default (trailing zeros dropped, so 1 km shows as 1000 m). You can choose Auto (up to 10 digits), fixed decimals or more significant figures, or switch to scientific or engineering notation.

Length converter