Screen Size Calculator

Display sizes are quoted as a diagonal measurement in inches. To recover width and height you need the aspect ratio. For 16:9 the diagonal-to-width factor is approximately 0.872, to height 0.490.

The calculator takes diagonal and aspect ratio and returns width, height, and total surface area. Supports 16:9, 16:10, 21:9, 4:3, 3:2, 1:1, and arbitrary ratios.

The diagonal convention is a CRT-era inheritance — measuring diagonal made comparison across different aspect ratios easier when 4:3 was standard. The math is straightforward Pythagoras: for a screen with width w and height h, diagonal d = √(w² + h²). Given aspect ratio a:b and diagonal d, width = d × a / √(a² + b²) and height = d × b / √(a² + b²). For 16:9, the denominator is √(256 + 81) = √337 ≈ 18.36, giving the factors 16/18.36 ≈ 0.872 and 9/18.36 ≈ 0.490.

A worked example: a 27-inch 16:9 monitor. Width = 27 × 0.872 = 23.54 inches, height = 27 × 0.490 = 13.24 inches, area = 311.6 square inches. The same 27-inch diagonal at 21:9 ultrawide ratio gives width = 24.84 inches, height = 10.65 inches, area = 264.5 square inches — same diagonal, less surface. A 32-inch 4:3 from the CRT era had width = 25.6 inches, height = 19.2 inches, area = 491.5 square inches — visibly larger than a 32-inch 16:9 widescreen at 437.7 square inches.

Limitations: the active display area excludes bezel, stand, and any trim. Modern thin-bezel monitors lose only a few millimeters per side, but immersive setups need physical dimensions for desk planning. Curved displays add a small correction (the diagonal is the chord of the arc, not the straight line) that the calculator ignores — for 1500R curvature on a 34-inch ultrawide, the error is under 0.5%. Pixel density and resolution are independent of physical size; a 27-inch 4K and 27-inch 1080p have the same physical dimensions.