Inches to Centimetres, and What an Inch Measures
Inches to centimetres is a multiplication: multiply by 2.54. The tool updates as you type, so you can check a product page or a size chart line by line.
Screens, pipes and heights
A 55-inch television measures 139.7 cm across the diagonal. A 16:9 panel is roughly 121.8 cm wide and 68.5 cm tall, excluding the bezel; check the manufacturer's overall dimensions before measuring a cabinet, because bezels add a few centimetres.
Pipes, threads and camera filters are often quoted in inches: 1/2 inch is 1.27 cm and 3/4 inch is 1.905 cm. A height written as 5 feet 10 inches becomes 70 inches, then 177.8 cm. Convert the feet first, never type 5.10.
- Convert a TV or monitor diagonal into centimetres
- Check pipe, thread and filter diameters
- Turn a height in feet and inches into centimetres
2.54 and feet-plus-inches
One inch is exactly 2.54 cm under the 1959 agreement, so one foot is 12 inches, or 30.48 cm. The tool multiplies by 2.54, keeps six decimals below 1,000 with trailing zeros removed, and two decimals at 1,000 or above.
For feet and inches, multiply the feet by 12 and add the inches before converting. A fractional inch such as 3/8 becomes 0.375 first. Typing 5.10 for 5 feet 10 inches gives 12.95 cm, which is the most common mistake in this conversion.
- 1 foot = 12 inches = 30.48 cm
- 5 ft 10 in is 70 inches, not 5.10
- Fractional inches: 3/8 becomes 0.375
A diagonal does not fix the shape
The same diagonal does not mean the same shape: a 55-inch 16:9 panel and a 55-inch 21:9 panel have very different widths and heights. The tool converts length only; it does not compute width, height, bezel or viewing distance.
The Chinese cun (about 3.33 cm) and the Japanese cun (about 3.03 cm) are not inches. Imported pipe fittings also differ in thread form, not just diameter, so match the standard rather than converting the number alone.
- Same diagonal, different ratio, different shape
- Market cun ≈ 3.33 cm; Japanese cun ≈ 3.03 cm
- Pipe threads need the standard, not just a length
FAQ
How big is a 55-inch TV screen?
55 inches is the diagonal, equal to 139.7 cm. A 16:9 panel measures roughly 121.8 cm wide by 68.5 cm tall, excluding the bezel. Check the manufacturer's overall dimensions before measuring a cabinet.
Is an inch the same as the Chinese cun?
No. An inch is exactly 2.54 cm, while the market cun is one tenth of a chi, about 3.33 cm, roughly 31% longer. Screen and pipe sizes usually mean inches; traditional furniture may use the cun.
How do I convert 5 feet 10 inches?
Multiply the feet by 12 and add the inches: 5 × 12 + 10 = 70 inches, then × 2.54 = 177.8 cm. Entering 5.10 as inches gives 12.95 cm, a common error; convert fractional inches to decimals first.
Related tool：Inches to CM