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Total Usage 1 times
55"
Diagonal139.7cm
Width (approx)121.8cm
Height (approx)68.5cm
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About

Purchasing a new television or monitor involves balancing specification desires with physical space constraints. Manufacturers universally market screens by their diagonal measurement in inches, yet furniture, wall mounts, and room layouts are often measured in the metric system (centimeters). This mismatch leads to return hassles when a "65-inch" TV fails to fit a 140cm niche.

This tool goes beyond simple unit conversion. It calculates the physical Width and Height of the screen based on the standard 16:9 aspect ratio used in virtually all modern HDTVs and 4K displays. By understanding the trigonometry of the display, users can plan their home theater or workstation setup with millimeter precision, accounting for the actual panel size before adding bezel allowances.

screen size tv dimensions monitor calculator inches to cm electronics

Formulas

The core conversion is a linear scaling factor, but the dimension extraction requires trigonometry based on the Pythagorean theorem.

Dcm = Dinch × 2.54

For a standard 16:9 aspect ratio, the angle θ is arctan(9/16). The dimensions are:

Width = Dcm × 0.8716

Height = Dcm × 0.4903

Reference Data

Diagonal (in)Diagonal (cm)Width (cm)Height (cm)Usage Class
13.333.829.416.6Compact Laptops
2461.053.129.9Standard Office Monitor
2768.659.833.6Gaming Monitor
3281.370.839.8Small Bedroom TV
55139.7121.868.5Living Room Standard
65165.1143.980.9Home Cinema Entry
75190.5166.093.4Large Format
85215.9188.2105.8Premium Theater

Frequently Asked Questions

No. This tool calculates the active screen area (the glass). You must add 2-5 cm to the width and height depending on the manufacturer's bezel design to get the total physical footprint.
No. Ultrawide monitors typically use a 21:9 ratio. This calculator assumes a standard 16:9 ratio found on most TVs and standard monitors. Using this for a 21:9 screen would result in incorrect Width/Height values.
Historically, early cathode ray tubes were circular, and the usable rectangular image was measured diagonally. The tradition stuck as a single number is easier to market than "Width x Height".
Measure from the top-left corner of the actual glass to the bottom-right corner. Do not include the plastic casing.