Convert centimeters to inches

The formula

inches = centimeters × 0.39370079

centimeters to inches — quick reference

Four inches is almost exactly ten centimetres, and that is the anchor to keep

Ten centimetres is 3.937 inches, under two per cent away from four, which turns the conversion into a ratio anyone can hold: divide the centimetres by ten, multiply by four. 25 cm gives 10 inches against a true 9.84; 60 cm gives 24 against 23.62. The answer is always slightly generous, so trim a couple of per cent from it.

Two fixed points sit alongside it. Roughly 2.5 cm is an inch, and 30 cm is a foot to within half a centimetre, which makes a metric tape usable for imperial estimates with no arithmetic at all - a 90 cm worktop is three feet to within a centimetre and a half.

The inch is exact by definition, but old measurements may predate the definition

Since the 1959 international yard and pound agreement the inch has been exactly 25.4 mm, settled between the English-speaking countries. Before it, the imperial and American inches differed by a couple of parts per million - meaningless for a shelf, real across a survey baseline. The US survey foot was only officially retired at the end of 2022.

Most centimetre-to-inch questions concern things whose imperial size is the official one. Screen diagonals are always inches, so a 140 cm television is a 55-inch; bicycle and car wheels are sized in inches at the rim even where the tyre itself is described in millimetres. Converting the metric measurement gives you the label, not a new size.

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