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Real TV and monitor dimensions, instantly.
Enter a screen's diagonal size in inches and its aspect ratio to get the physical width and height. Useful when a TV or monitor will not fit the cabinet, or when comparing how much bigger a 55" really is than a 50". Defaults to the standard 16:9 widescreen ratio.
Screen size is the diagonal measurement in inches — a 55-inch TV measures 55 inches corner to corner, not across. Combined with the aspect ratio, the diagonal determines the actual width and height through the Pythagorean theorem: for a 16:9 screen, width = diagonal x 16/√337 and height = diagonal x 9/√337 (since 16² + 9² = 337). A 55-inch 16:9 TV is therefore about 47.9 inches wide and 27.0 inches tall — numbers that matter enormously when checking whether it fits the wall unit.
Screen area grows with the square of the diagonal, so size upgrades are bigger than they sound: a 65-inch TV has (65/55)² = 1.397, or about 40 percent more screen area than a 55-inch, not the 18 percent the diagonal suggests. This is why the jump from 55 to 65 feels dramatic in the living room. Viewing distance guidance scales with size too: for 4K, 1 to 1.5 times the diagonal; for 1080p, 1.5 to 2.5 times — a 55-inch 4K TV wants you 55 to 82 inches away, close enough that the extra pixels are actually visible.
Phones, monitors, and TVs all use the same diagonal convention, but aspect ratios vary: phones are tall (19.5:9 common), monitors are 16:9 or 21:9 ultrawide, TVs are 16:9. Compare screens by width and height (or area), never by diagonal alone across different ratios — a 34-inch 21:9 ultrawide is shorter than a 32-inch 16:9 monitor despite the bigger number.
Width = diagonal × ratio-width ÷ √(ratio-width² + ratio-height²), and likewise for height — straight from the Pythagorean theorem.
The divisor: √(16² + 9²) = √337 = 18.3576. Width: 55 x 16 / 18.3576 = 880 / 18.3576 = 47.94 inches. Height: 55 x 9 / 18.3576 = 495 / 18.3576 = 26.97 inches. So the panel is about 47.9 x 27.0 inches — add 1 to 2 inches all around for the bezel and stand when measuring furniture. Screen area: 47.94 x 26.97 = 1,292.9 sq in. Sanity check against a 65-inch: (65/55)² = 1.397 times the area, or about 1,806 sq in — the 10 extra diagonal inches buy 40 percent more screen.
Width: 27 x 16 / 18.3576 = 432 / 18.3576 = 23.53 inches. Height: 27 x 9 / 18.3576 = 243 / 18.3576 = 13.24 inches. A dual-27-inch setup therefore spans about 47 inches wide plus bezels — measure the desk before buying the second monitor. Compare with a 34-inch 21:9 ultrawide: divisor √(21² + 9²) = √522 = 22.847; width 34 x 21/22.847 = 31.25 in, height 34 x 9/22.847 = 13.40 in — wider but barely taller than the 27-inch, which is exactly the ultrawide trade-off.
No — diagonal size is measured corner to corner. A 55" TV is roughly 48" wide and 27" tall in 16:9; our calculator shows the real dimensions.
Measure the visible screen corner to corner with a tape measure, or check the manufacturer's specifications — the advertised size is the screen, not the frame.
For 4:3, enter 4 and 3 as the ratio. For ultrawide monitors, enter 21 and 9. The math works for any ratio you type.