UnitPairs

inches to centimetres converter

1 in = 2.54 cm. Type a value in either box — the other side updates instantly, using the exact definition factor, not a rounded shortcut. Screen sizes, tyre sidewalls and US tape measures are marked in inches; the rest of the world reads them in centimetres.

Rate: 1 in = 2.54 cm · 1 cm = 0.3937007874 in · As a tape-measure fraction:

Inches as fractions

Tape measures and rulers are marked in sixteenths of an inch, not decimals. For the worked example on this page, 12 in is closest to 12 in — the fraction is an approximation, off by 0.00e+0 in (about 0 mm). The fraction readout in the converter above updates with whatever you type, so you can read any result straight onto a ruler.

Formula and a worked example

centimetres = inches × 2.54. Worked example: 12 in × 2.54 = 30.48 cm. To go back, divide by the same factor (or multiply by 0.3937007874).

Where the factor comes from: The inch is defined as exactly 2.54 centimetres (25.4 mm) under the 1959 international yard and pound agreement. Factors on UnitPairs follow the NIST definitions, so results agree between pages to the last digit shown.

inches to centimetres chart

inches (in)centimetres (cm)
12.54
25.08
37.62
410.16
512.7
615.24
820.32
1025.4
1230.48
1845.72
2460.96
3691.44
48121.92
60152.4
72182.88

Questions

How many centimetres are in one inche?

Exactly 2.54 cm — that is the rate this converter applies in both directions.

How do I convert in to cm by hand?

Multiply the inches value by 2.54. For a rough mental estimate, 2.54 is usually close enough — but use the full factor for anything you plan to build, buy or dose.

How accurate is this converter?

The factors are the exact international definitions, so the only rounding is in the display — results are shown to six decimal places, and the underlying value is never pre-rounded.

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