Length converter
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.
1 centimetre = 0.3937 inches
How it’s calculated
in = cm ÷ 2.54
- Divide the value in centimetres by 2.54.
- Equivalently, multiply by 0.3937007874.
- 1 cm = 0.3937007874 in · 1 in = 2.54 cm
Show worked solutionFactor, unit cancellation and rounding, step by step
Find the conversion factor
By definition 1 cm = 0.01 m and 1 in = 0.0254 m, so 1 in = 2.54 cm. Source: BIPM SI Brochure (9th ed.); NIST SP 811 / Handbook 44.
Multiply by the factor written as a fraction
Put cm in the denominator so it cancels, leaving in.
Calculate (unrounded)
Round the answer
Rounded to 5 significant figures.
Answer: 0.3937 in
1 cm in other units
Batch convert cm → in
- 1 cm = 0.3937 in
- 5 cm = 1.9685 in
- 10 cm = 3.937 in
- 25 cm = 9.8425 in
Common length conversions
Length units and exact definitions
| Unit | System | Definition |
|---|---|---|
| Metre (m) | SI (metric) | Base unit |
| Kilometre (km) | SI (metric) | 1 km = 1000 m |
| Centimetre (cm) | SI (metric) | 1 cm = 0.01 m |
| Millimetre (mm) | SI (metric) | 1 mm = 0.001 m |
| Micrometre (µm) | SI (metric) | 1 µm = 0.000001 m |
| Nanometre (nm) | SI (metric) | 1 nm = 1e-9 m |
| Inch (in) | US & imperial (identical) | 1 in = 0.0254 m |
| Foot (ft) | US & imperial (identical) | 1 ft = 0.3048 m |
| Yard (yd) | US & imperial (identical) | 1 yd = 0.9144 m |
| Mile (mi) | US & imperial (identical) | 1 mi = 1609.344 m |
| Nautical mile (nmi) | other | 1 nmi = 1852 m |
| Mil (thou) (mil) | US & imperial (identical) | 1 mil = 0.0000254 m |
| US survey foot (ft (US survey)) | US customary | 1 ft (US survey) = 0.3048006096 m |
| Astronomical unit (au) | other | 1 au = 149597870700 m |
| Light-year (ly) | other | 1 ly = 9.460730473e15 m |
| Ångström (Å) | other | 1 Å = 1e-10 m |
Centimetres to inches conversion table
| 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.