Inch to Centimeter
Convert inch (in) to centimeter (cm) instantly. Switch between metric and imperial in a tap.
Inch → Centimeter
2.54
cm
1 in = 2.54 cm
Frequently asked questions
Exactly 2.54 centimetres, by international definition. The conversion is a single multiplication and carries no rounding error.
Convert the fraction to a decimal first, then multiply by 2.54. Three-quarters of an inch is 0.75 × 2.54 = 1.905 cm. Common values: 1/8 in is 0.3175 cm, 1/4 in is 0.635 cm, 1/2 in is 1.27 cm and 3/4 in is 1.905 cm.
Because nominal pipe size is a conventional label rather than a dimension. The actual internal and external diameters come from the standard for that pipe schedule and material, not from the name. The same applies to timber sizes and screw gauges — where a fit matters, measure the component rather than converting the label.
Multiply by 2.54
An inch is exactly 2.54 centimetres. The conversion is a single multiplication with no rounding error, since the relationship is defined rather than measured.
Centimetres = inches × 2.54
The conversions that come up most
Screen sizes, which are quoted in diagonal inches everywhere. Converting to centimetres is what tells you whether a television fits the space:
- 32 in = 81.3 cm diagonal
- 43 in = 109.2 cm
- 55 in = 139.7 cm
- 65 in = 165.1 cm
Remember these are diagonals. For a 16:9 screen, width is roughly the diagonal × 0.87 and height × 0.49 — so a 55-inch television is about 121.8 cm wide, not 139.7.
Clothing sizes. Indian retail commonly labels waist and chest in inches while size charts give centimetres:
- 28 in waist = 71.1 cm
- 32 in = 81.3 cm
- 36 in = 91.4 cm
- 40 in = 101.6 cm
Hardware and plumbing. Pipe and fitting sizes in India remain largely imperial — a half-inch pipe is nominally 1.27 cm, though nominal pipe sizes are conventional labels rather than exact internal diameters, which is a separate complication worth knowing before buying fittings.
Feet and inches together
A height given as feet and inches needs the feet converted first:
5 feet 9 inches = (5 × 12) + 9 = 69 inches, then 69 × 2.54 = 175.3 cm.
Multiplying the feet by 30.48 and adding the inches × 2.54 gives the same answer: 152.4 + 22.86 = 175.26 cm.
Fractional inches
Imperial measurements frequently use fractions rather than decimals, particularly in hardware:
- 1/8 in = 0.3175 cm
- 1/4 in = 0.635 cm
- 3/8 in = 0.9525 cm
- 1/2 in = 1.27 cm
- 5/8 in = 1.5875 cm
- 3/4 in = 1.905 cm
- 7/8 in = 2.2225 cm
Convert the fraction to a decimal first, then multiply. Three-quarters of an inch is 0.75 × 2.54 = 1.905 cm.
A mental approximation
Multiply by 2.5 and add a little. For 40 inches: 40 × 2.5 = 100, plus about 1.6, gives 101.6 cm — which is exact in this case. The 2.5 shortcut is within 1.6% for any value.
Nominal sizes are labels, not measurements
A caution specific to hardware. Nominal pipe size is a conventional label rather than a dimension you can convert. A "half-inch" pipe does not have a half-inch internal or external diameter — the designation is historical, and the actual dimensions come from the relevant standard for that pipe schedule and material.
The same applies to timber, where a "2 by 4" is nominally two inches by four and actually smaller after planing, and to screw gauges, where the number refers to a gauge scale rather than a diameter.
Converting these labels arithmetically produces a number that is correct as arithmetic and wrong as a measurement. Where a fit matters, measure the actual component rather than converting the name on the box.