Screen Size Calculator

How width and height are calculated

A manufacturer names one diagonal, and the width and height follow from the aspect ratio by the Pythagorean theorem. A 55-inch TV with a 16:9 screen has a visible area of 121.8 × 68.5 cm. The bezel adds a few centimeters on each side; check the model's specs for the full cabinet size.

"21:9" monitors actually come in two proportions: 2560 × 1080 pixels give 64:27, while 3440 × 1440 gives 43:18. If you calculate a 34-inch screen as exactly 21:9, the height comes out 7 mm larger than the real one. That is why the list includes both variants, and the ratio is taken exactly from the resolution.

Recommended viewing distance

THX recommends sitting far enough back that the screen fills about 40 degrees of your field of view. The 30-degree figure is often attributed to SMPTE, though its standards contain no such direct recommendation. A third number shows where your neighbors' pixels stop being distinguishable at a visual acuity of one arc minute, and it depends on the resolution.