maratoolHow to calculate TV and monitor dimensions from the diagonal
Enter a diagonal and aspect ratio — read true width, height, area, and PPI.
A "55-inch" TV tells you one number — the diagonal. The Screen Size Calculator turns it into shelf-fitting width and height, viewing area, and pixel density.
How it works
- Diagonal — the marketing size in inches.
- Aspect ratio — 16:9 unless you know otherwise.
- Optional resolution — adds PPI to the readout.
The formula
For ratio w:h, width = diag × w/√(w²+h²) and height = diag × h/√(w²+h²). For 16:9 that means width = 0.8716 × diag and height = 0.4903 × diag — a 65″ TV is 56.7″ × 31.9″ (144 × 81 cm) plus bezel.
Diagonal inflation
Wider ratios pack less area per diagonal inch: a 34″ 21:9 ultrawide has about the same height as a 27″ 16:9 monitor, just stretched sideways. Compare areas, not diagonals, when weighing formats.
Sources & methodology
The formula is arithmetic stated inline above — no external dataset is involved. Everything runs client-side in your browser; nothing is uploaded.
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