Convert Inches to CM

Inches to centimetres – decimals, fractions and heights

Type a length in inches and the converter shows it in centimetres immediately, together with millimetres, metres, feet and every other length unit. It also rounds your value to the nearest sixteenth of an inch and splits long lengths into feet and inches, so you can check that the number you typed matches what is on your tape measure. A swap button turns the tool round for centimetres to inches.

The conversion is exact: one inch is defined as 2.54 centimetres (25.4 mm). Any decimals you see beyond that come only from the length you entered, not from an approximation in the factor.

The formula

cm = inches × 2.54

mm = inches × 25.4

inches = cm ÷ 2.54

For a height written in feet and inches, first turn it into inches (feet × 12 + inches), then multiply by 2.54. Example: 5 ft 9 in = 69 in; 69 × 2.54 = 175.26 cm.

Converting fractions of an inch

Tape measures, drill bits, spanners and timber in the US are labelled in fractions. Turn the fraction into a decimal first – divide the top number by the bottom number – then multiply by 2.54. 3/8 in = 0.375 in = 0.9525 cm (9.5 mm). 5 3/4 in = 5.75 in = 14.605 cm. You can type the decimal straight into the converter; the result line shows the nearest 1/16 so you can confirm the fraction you meant.

Worked examples

• 12 in (1 ft) × 2.54 = 30.48 cm.
• A 6.1 inch phone screen × 2.54 = 15.49 cm diagonal.
• A 55 inch TV × 2.54 = 139.7 cm diagonal (about 121.8 × 68.5 cm for a 16:9 screen).
• A 32 inch waist × 2.54 = 81.28 cm.
• US Letter paper 8.5 × 11 in = 21.59 × 27.94 cm.
• A 4 × 6 inch photo = 10.16 × 15.24 cm.
• A 26 inch bicycle wheel = 66.04 cm nominal diameter.

Inches to centimetres chart

Height chart: feet and inches to cm

Quick mental estimate

Multiply inches by 2.5 and add a bit: 10 in × 2.5 = 25, real answer 25.4 cm. For larger numbers, multiply by 2.5 and then add 1.6% – 40 in × 2.5 = 100, plus 1.6 = 101.6 cm, which is exact. A foot is a little over 30 cm, and a yard (36 in) is a little under a metre (91.44 cm).

Screens: why sizes are quoted in inches

TV, monitor, laptop and phone screens are sold by their diagonal measurement in inches almost everywhere in the world, even in countries that use the metric system for everything else. To know whether a TV will fit a cabinet you need its width and height, which depend on the aspect ratio. For 16:9 screens, width ≈ diagonal × 0.872 and height ≈ diagonal × 0.490. So a 65 in TV (165.1 cm diagonal) is about 143.9 cm wide and 80.9 cm tall without the bezel and stand.

Inches in clothing and shoe sizes

US and UK jeans are sized by waist and inseam in inches (for example 32 × 30). To compare with European sizes, convert both: 32 in = 81.3 cm waist, 30 in = 76.2 cm inseam. Bra band sizes in the US and UK are also in inches (34 = 86 cm band), whereas EU sizes use centimetres in steps of 5 (75, 80, 85). Ring sizes, hat sizes and glove sizes have their own systems, but all can be checked by converting the measured circumference.

Where the inch comes from

The inch is one of the oldest units still in use. Anglo-Saxon and later English law defined it as three barleycorns laid end to end, and in many European languages the word for inch is the same as the word for thumb. Different countries used slightly different inches until 1959, when the international yard and pound agreement fixed the inch at exactly 25.4 mm. The US kept a 'survey inch' for land measurement until 2022; it differed from the international inch by only two parts per million.

Accuracy and rounding

For everyday use, one decimal place in centimetres (a millimetre) is enough. Engineers working in inches often specify tolerances in thousandths of an inch (0.001 in = 0.0254 mm), so keep at least three decimals in millimetres when converting technical drawings. The converter displays up to eight significant figures so you can round as precisely as your task requires.

Privacy

The converter runs entirely in your browser. Nothing you type is sent to a server, your values are not tracked, and once the page has loaded it keeps working offline – useful in a workshop, a kitchen, a gym or on a plane.

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