Inches to CM Converter

How do you convert inches to centimetres?

Multiply the number of inches by 2.54. That single step gives centimetres, and because 2.54 is an exact definition rather than a rounded figure, any error in your answer comes only from how you round at the end.

centimetres = inches × 2.54

Take a 27-inch computer monitor: 27 × 2.54 = 68.58 cm, measured diagonally across the screen. For millimetres, multiply by 25.4 instead, so a ¾-inch board is 19.05 mm thick. If you have feet and inches, turn everything into inches first: 2 ft 3 in is 27 inches, which is the same 68.58 cm.

A quick mental check helps catch slips. Two and a half centimetres per inch gets you close, so 40 inches should come out a little over 100 cm. The exact answer is 101.6 cm.

Inches to cm chart: 1 to 100 inches

Every value in this chart is exact to two decimal places, because each inch adds exactly 2.54 cm. Print it or keep it open beside a tape measure.

How do you convert tape-measure fractions to cm?

Multiply the fraction by 25.4 to get millimetres, then divide by 10 for centimetres. Imperial tapes and rulers split each inch into halves, quarters, eighths and sixteenths. The table gives the exact millimetre value of every sixteenth, plus centimetres rounded to two places, so you can read an imperial tape and order in metric.

For a mixed reading such as 5 ⅜ inches, convert the whole and the fraction separately and add them: 5 × 2.54 = 12.7 cm, plus 0.95 cm, gives 13.65 cm. The guide on how to read a tape measure explains the markings themselves.

Everyday UK examples in inches and centimetres

Inches turn up more often in British life than many people expect. These are some of the measurements people most often need in centimetres.

Where are inches still used in the UK?

Screens of every kind are sold by their diagonal in inches, and so are many computer monitors and tablets. Clothing for men is still commonly sized in inches, from 32-inch waist jeans to 15½-inch shirt collars, and most people know their own height in feet and inches. Car and bicycle wheels are described by rim size in inches, as in the R16 part of a tyre size, and plumbing threads keep inch-based names such as ½-inch BSP. For the reverse calculation, the cm to inches converter divides by 2.54 instead, and the length conversions guide covers feet, yards and miles too.

Frequently asked questions

How many cm is 1 inch?

One inch is exactly 2.54 centimetres, or 25.4 millimetres. The figure is a definition agreed internationally in 1959, not a rounded value.

How many cm is 12 inches?

Twelve inches, which is one foot, is exactly 30.48 cm. That is just over the length of a standard 30 cm ruler.

Is 2.5 close enough when converting inches to cm?

For a rough estimate, yes, but it undercounts by about 1.6 per cent. On 60 inches it gives 150 cm instead of the correct 152.4 cm.

How do I convert inches to millimetres?

Multiply inches by 25.4. For example, half an inch is 12.7 mm and 3 inches is 76.2 mm.

How many centimetres is a 55-inch TV?

A 55-inch TV measures 139.7 cm diagonally from corner to corner of the screen. The width and height are smaller and depend on the shape of the screen.

Related converters

• CM to inches
• Feet to CM
• CM to feet
• Length converter
• Size charts

See the full length converter for every unit in this family, or browse our guide to units of measurement.