Pick an aspect ratio, then enter a diagonal, width, or height. The tool resolves the other two dimensions in inches and centimeters.
Screen Size Calculator is a free, browser-based screen testing tool that runs the full check instantly in your web browser.
TV and monitor marketing leads with the diagonal — "55-inch TV", "27-inch gaming monitor" — because it's one memorable number. But the diagonal alone doesn't tell you whether the screen fits your space or compares meaningfully to another product. A 55-inch 16:9 TV is 48 inches wide and 27 inches tall. A 55-inch 21:9 ultrawide monitor is 51 inches wide and 22 inches tall. Same diagonal, very different real estate on your desk or wall.
Every screen is a rectangle with a fixed aspect ratio (width:height). If you know the aspect ratio and any one of diagonal, width, or height, basic trigonometry solves the other two:
The calculator runs this live as you type and converts both ways between inches and centimeters.
Two TVs with the same diagonal but different aspect ratios display different amounts of content. Visible area (width × height) is the best single number for "how much screen you actually get." A 27-inch 16:9 monitor has 311 square inches of screen. A 32-inch 16:9 monitor has 438 — about 40% more. A 34-inch 21:9 ultrawide has 424 — nearly the same area as the 32-inch flat panel but much wider and shorter.
Before ordering a new TV, measure the wall or cabinet width you have. Use this calculator to confirm the advertised diagonal fits. A "75-inch TV" is 65.4 inches wide (for 16:9) — it might not fit a 60-inch-wide media stand. Also factor in the TV bezel (usually +0.5 to +2 inches on each side) and any stand or wall-mount hardware.
Screen Size Calculator FAQ
