calcanswers.com All calculators

CM to Inches and Inches to CM

Conversions

Choose a direction and enter the length. The converter uses the exact definition, 1 inch = 2.54 cm. For inches to cm it also shows the width and height of a 16:9 screen with that diagonal.

Convert

Use a period for decimals, like 12.5. Commas for thousands are fine. The result updates as you type.Decimals with a period, like 12.5

Your entries stay on your device. The math runs right in your browser.

Result: In inches

11.811in

30 cm is 11.811 in.

Step by step

30 / 2.54 = 11.811 in

  1. One inch is exactly 2.54 cm, so divide by 2.54: 30 / 2.54 = 11.811 in.
  2. Check: 11.811 × 2.54 gives back about 30 cm.

Formula

inches = cm / 2.54 = mm / 25.4
inches
length in inches (in or ″)
cm, mm
length in centimeters or millimeters

How it works

Since 1959 the inch has been defined as exactly 2.54 centimeters, the same in the United States, the UK and everywhere else. To convert inches to cm, multiply by 2.54: 12 inches are 30.48 cm. To convert cm to inches, divide by 2.54: 30 cm are 11.811 inches. One millimeter is a tenth of a centimeter, so for mm to inches you divide by 25.4.

Rulers and tape measures in the US show inches in fractions, usually down to 1/16 inch. To read a decimal result on a ruler, multiply the decimal part by 16 and round: 11.811 inches is 11 inches plus 0.811 × 16 = 12.98, so about 11 13/16 inches. One sixteenth of an inch is 1.5875 mm, which is the accuracy of that reading.

TVs and monitors are sold by their diagonal in inches. For inches to cm the converter also gives the picture width and height of a 16:9 screen, the shape of nearly all TVs, using the Pythagorean theorem: width = diagonal × 16 / √337 and height = diagonal × 9 / √337. A 55 inch TV has a picture about 121.8 cm wide and 68.5 cm tall (about 48 by 27 inches); the frame adds a little. For heights in feet and inches, use the feet to cm converter.

The formula

The factor 2.54 is exact, so results are exact up to the shown decimals. Dividing by 2.54 is the same as multiplying by 0.393700787..., which is why 1 cm is about 0.3937 inch.

The screen formula assumes square pixels and a 16:9 picture. Older 4:3 screens and ultrawide 21:9 monitors have different shapes, so their width and height differ for the same diagonal.

Example

How big is a 55 in TV in centimeters?

  1. Diagonal in centimeters: 55 × 2.54 = 139.7 cm.
  2. Picture width at 16:9: 139.7 × 16 / √337 = 121.8 cm.
  3. Picture height at 16:9: 139.7 × 9 / √337 = 68.5 cm. The TV with its frame is a few millimeters to a few centimeters larger.

55 in is 139.7 cm, or 1,397 mm.

Load this example into the calculator

Inches to cm chart: lengths and TV screen sizes

Length in inchesIn centimetersScreen width at 16:9Screen height at 16:9
1 in2.54 cm2.2 cm1.2 cm
2 in5.08 cm4.4 cm2.5 cm
3 in7.62 cm6.6 cm3.7 cm
4 in10.16 cm8.9 cm5 cm
5 in12.7 cm11.1 cm6.2 cm
6 in15.24 cm13.3 cm7.5 cm
7 in17.78 cm15.5 cm8.7 cm
8 in20.32 cm17.7 cm10 cm
9 in22.86 cm19.9 cm11.2 cm
10 in25.4 cm22.1 cm12.5 cm
11 in27.94 cm24.4 cm13.7 cm
12 in30.48 cm26.6 cm14.9 cm
13.3 in33.782 cm29.4 cm16.6 cm
14 in35.56 cm31 cm17.4 cm
15.6 in39.624 cm34.5 cm19.4 cm
17.3 in43.942 cm38.3 cm21.5 cm
19 in48.26 cm42.1 cm23.7 cm
21.5 in54.61 cm47.6 cm26.8 cm
22 in55.88 cm48.7 cm27.4 cm
24 in60.96 cm53.1 cm29.9 cm
27 in68.58 cm59.8 cm33.6 cm
32 in81.28 cm70.8 cm39.8 cm
34 in86.36 cm75.3 cm42.3 cm
40 in101.6 cm88.6 cm49.8 cm
42 in106.68 cm93 cm52.3 cm
43 in109.22 cm95.2 cm53.5 cm
48 in121.92 cm106.3 cm59.8 cm
50 in127 cm110.7 cm62.3 cm
55 in139.7 cm121.8 cm68.5 cm
58 in147.32 cm128.4 cm72.2 cm
60 in152.4 cm132.8 cm74.7 cm
65 in165.1 cm143.9 cm80.9 cm
70 in177.8 cm155 cm87.2 cm
75 in190.5 cm166 cm93.4 cm
77 in195.58 cm170.5 cm95.9 cm
83 in210.82 cm183.7 cm103.4 cm
85 in215.9 cm188.2 cm105.8 cm
98 in248.92 cm217 cm122 cm
100 in254 cm221.4 cm124.5 cm

Frequently asked questions

How many inches is 30 cm?

30 cm is 11.81 inches (30 / 2.54), just under a foot. A foot is 12 inches, which is 30.48 cm. Other common values: 10 cm = 3.94 inches, 50 cm = 19.69 inches, 100 cm = 39.37 inches.

How many centimeters are in an inch?

Exactly 2.54 centimeters, or 25.4 millimeters. This has been the international definition since 1959. So 2 inches are 5.08 cm, 6 inches 15.24 cm and 10 inches 25.4 cm.

How do I convert mm to inches?

Divide the millimeters by 25.4. 10 mm are 0.394 inch, 12 mm are 0.472 inch and 25 mm are 0.984 inch, just under one inch. Bolt and drill sizes are a common reason to need this.

How do I write a decimal inch as a fraction?

Multiply the decimal part by 16 (or 8, or 32) and round to a whole number. 0.375 inch × 16 = 6, so 6/16 = 3/8 inch. 2.7 inches: 0.7 × 16 = 11.2, so about 2 11/16 inches.

How wide is a 65 inch TV?

A 65 inch 16:9 TV has a picture about 143.9 cm (56.7 inches) wide and 80.9 cm (31.9 inches) tall. The diagonal is 165.1 cm. Add a few centimeters for the frame when you plan a wall or a cabinet.

Last updated: Responsible editor: Jared Alan
Checked against 23 test cases · How we test
Sources: