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Inches to Centimetres
To convert inches to centimetres, multiply by 2.54, because an inch is exactly 2.54 cm. 55 inches × 2.54 = 139.7 cm, exactly. If 55 inches is a TV’s diagonal, its 16:9 picture is about 121.8 cm wide and 68.5 cm tall. Fractions of an inch convert exactly too.
Type inches.
| Shown as | Value |
|---|---|
| Centimetres | 139.7 cm |
| Millimetres | 1,397 mm |
| Feet and inches | 4 ft 7 in |
| If it is a 16:9 screen’s diagonal: width | 121.8 cm |
| If it is a 16:9 screen’s diagonal: height | 68.5 cm |
The figures above are an example: put in your own. Fractions such as 5 3/8 or 5-3/8 work. Worked out in this browser and kept there; nothing is sent anywhere.
Type inches as a whole number, a decimal or a fraction such as 5 3/8, and read centimetres and millimetres. For a screen size, the table also gives the width and height of a 16:9 picture.
Inches to centimetres is a multiplication by 2.54, the exact number of centimetres in an inch since 1959. The result always ends, so a whole number of inches needs no rounding.
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- Nothing uploaded
- Exact factors
- Works offline
- Says when it rounds
Key facts
| Detail | Answer |
|---|---|
| Formula | cm = inches × 2.54 |
| Example | 55 in = 139.7 cm exactly |
| 1 inch | 2.54 cm, 25.4 mm, exactly |
| 12 inches | 30.48 cm |
| Screen sizes | Diagonal; a 55″ 16:9 picture is 121.8 × 68.5 cm |
| Where your numbers are kept | This browser only |
How to convert inches to centimetres
One multiplication; the converter also handles fractions.
Write the inches as a number
5 3/8 inches is 5.375.
Multiply by 2.54
5.375 × 2.54 = 13.6525 cm.
Round if you need to
To a millimetre: 13.7 cm.
For a screen, find the width
Multiply the diagonal by 0.8716 for 16:9.
Check the size
Centimetres should be about two and a half times the inches.
Who converts inches to centimetres
People with an inch figure who think, buy or build in metric.
TV and monitor buyers
A 65-inch set against a 150 cm unit.
Laptop and tablet shoppers
A 13.3-inch screen and a bag in cm.
Cyclists
Wheel sizes in inches, tyres in millimetres.
Woodworkers
An American plan cut in a metric workshop.
Photographers and framers
8 × 10 and 5 × 7 inch prints in cm.
Students
Science work that must be in SI units.
Screen sizes: the diagonal in cm, and the width it really means
The most common inch figure people convert is a screen size, and it is the one most often misread. A screen is sold by its diagonal, corner to corner across the visible picture. A 55-inch television is 139.7 cm across the diagonal, but it is not 139.7 cm wide: a 16:9 screen’s width is 16/√337 of its diagonal, about 87%, so the picture is about 121.8 cm wide and 68.5 cm tall. The cabinet adds its bezel and stand on top of that.
| Diagonal | Diagonal in cm | Picture width × height (cm) |
|---|---|---|
| 13.3″ | 33.8 cm | 29.4 × 16.6 cm |
| 15.6″ | 39.6 cm | 34.5 × 19.4 cm |
| 24″ | 61 cm | 53.1 × 29.9 cm |
| 27″ | 68.6 cm | 59.8 × 33.6 cm |
| 32″ | 81.3 cm | 70.8 × 39.8 cm |
| 43″ | 109.2 cm | 95.2 × 53.5 cm |
| 50″ | 127 cm | 110.7 × 62.3 cm |
| 55″ | 139.7 cm | 121.8 × 68.5 cm |
| 65″ | 165.1 cm | 143.9 × 80.9 cm |
| 75″ | 190.5 cm | 166.0 × 93.4 cm |
| 85″ | 215.9 cm | 188.2 × 105.8 cm |
To check a TV fits a unit, measure the space and compare it with the width column, then add the maker’s bezel figure, usually given on the specification sheet in millimetres. Phones are taller than 16:9 (around 19.5:9 for many), so their width is a smaller share of the diagonal, and the converter’s screen rows apply to televisions and monitors only. Laptop screens at 16:10 are also a little narrower than the table shows.
Inch sizes that are not their size
Many things sold in inches are not that size. The inch figure is a name, kept from an older way of making the thing, and converting it to centimetres gives a number you cannot measure. Convert the actual size instead.
| Sold as | Sounds like | Actually measures | In cm |
|---|---|---|---|
| 2×4 timber (US) | 2 × 4 in | 1½ × 3½ in, planed | 3.81 × 8.89 |
| ½-inch pipe (NPS) | ½ in | 0.840 in outside diameter | 2.13 |
| 29er or 700c bicycle wheel | 29 in | 622 mm rim bead seat | 62.2 (24.49 in) |
| 26-inch mountain bike wheel | 26 in | 559 mm rim bead seat | 55.9 (22.01 in) |
| “65-inch” TV | 65 in wide | 65 in diagonal; 143.9 cm wide | 165.1 diagonal |
Timber is planed after it is cut and dries smaller, which is why the American Softwood Lumber Standard sells a dressed 2×4 at 1½ by 3½ inches. Pipe sizes name a bore that the wall thickness has long since changed. Bicycle wheels are now specified by the bead seat diameter in millimetres from ISO 5775, printed on the tyre (622 for 700c and 29-inch), which is the number to trust.
Inches to centimetres chart, exact
Inches to centimetres is the friendly direction. Because an inch is exactly 2.54 cm, every whole number of inches, and every fraction of one with a 2, 4, 8, 16 or 32 underneath, converts to a centimetre figure that ends. Nothing in this table is rounded.
| Inches | Centimetres | Millimetres |
|---|---|---|
| 1/8 in | 0.3175 cm | 3.175 mm |
| 1/4 in | 0.635 cm | 6.35 mm |
| 1/2 in | 1.27 cm | 12.7 mm |
| 1 in | 2.54 cm | 25.4 mm |
| 2 in | 5.08 cm | 50.8 mm |
| 3 in | 7.62 cm | 76.2 mm |
| 4 in | 10.16 cm | 101.6 mm |
| 6 in | 15.24 cm | 152.4 mm |
| 8 in | 20.32 cm | 203.2 mm |
| 10 in | 25.4 cm | 254 mm |
| 12 in | 30.48 cm | 304.8 mm |
| 18 in | 45.72 cm | 457.2 mm |
| 24 in | 60.96 cm | 609.6 mm |
| 36 in | 91.44 cm | 914.4 mm |
To do it in your head, multiply by 2.5 and add a little: 12 inches is 30, plus 12 × 0.04 = 0.48, so 30.48 cm. The added part is always 4 hundredths of the inch figure. For printing, where a page is set in inches and a printer quotes millimetres, the KDP margin calculator and the trim size chooser give both.
What this converter does not do
This converts inches to centimetres. The screen rows assume a 16:9 picture and the diagonal of the visible area, and they are rounded to a millimetre. For a fraction of an inch you want in millimetres with a nearest metric size, the inch to mm converter is the better page; for feet as well as inches, use the height converter or the length converter. Negative lengths are refused.
This converter or a plain one
What this page adds to a typical one-formula converter.
| This converter | A typical converter | |
|---|---|---|
| Fractions of an inch | 3/8, 5 3/8 and 5-3/8 | Decimals only |
| Screen sizes | 16:9 width and height from the diagonal | The diagonal only |
| Nominal sizes explained | 2×4, pipe, wheels | Not mentioned |
| Exact or rounded | Says which | Unlabelled |
| Your entries leave the browser | Never | Varies |
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Frequently asked questions
How many cm is 55 inches?
55 inches is exactly 139.7 cm. If it is a television’s size, that is the diagonal of the picture; a 16:9 screen of that size is about 121.8 cm wide and 68.5 cm tall, before the frame. A 65-inch screen is 165.1 cm diagonally and about 143.9 cm wide.
How do you convert inches to cm?
Multiply the inches by 2.54. 12 inches × 2.54 = 30.48 cm. For a fraction, turn it into a decimal first: 3/4 inch is 0.75, and 0.75 × 2.54 = 1.905 cm. The converter accepts the fraction as you would write it, including 5-3/8.
How are TV sizes measured?
By the diagonal of the visible screen, corner to corner, in inches. The width is smaller: for the 16:9 shape of nearly every television it is 16/√337 of the diagonal, about 87%. A 55-inch TV is about 48 inches (121.8 cm) wide, before the bezel.
How many cm is 12 inches?
12 inches, one foot, is exactly 30.48 cm. A 30 cm ruler is therefore about 5 mm short of a foot, and the two are not interchangeable for anything that must fit. Two feet is 60.96 cm and three feet, a yard, is 91.44 cm.
How many cm is 6 inches?
6 inches is exactly 15.24 cm. It is a common length for a small ruler, a sub sandwich and a phone, though a phone’s 6-inch figure is its screen diagonal, not its body. Half of it, 3 inches, is 7.62 cm.
Why is a 2x4 not 2 inches by 4 inches?
Because the name is the rough-sawn size. Timber is dried and planed after sawing, and the American Softwood Lumber Standard sells a dressed 2×4 at 1½ by 3½ inches, which is 3.81 by 8.89 cm. Convert the actual size, not the name.
How many cm is a 29-inch bike wheel?
Not 73.66 cm. A 29er, like a 700c road wheel, has a rim with a 622 mm bead seat diameter under the ISO 5775 system, which is 24.49 inches; the 29 describes the rough outside diameter with a tyre fitted. The 622 is printed on the tyre wall and is the number to match.
Related guides
Where the inch still sets the page.