How screen size is calculated step-by-step
A display panel's diagonal, width, and height form a right triangle. Using the Pythagorean theorem combined with the aspect ratio ($w:h$), we can derive exact height and width from the diagonal ($d$):
Height = d ÷ √(1 + (w ÷ h)²) Width = Height × (w ÷ h) Screen Area = Width × Height Example: 55-inch TV with 16:9 Aspect Ratio Height = 55 ÷ √(1 + (16 ÷ 9)²) = 26.96 inches Width = 26.96 × (16 ÷ 9) = 47.94 inches Area = 47.94 × 26.96 = 1,292.5 sq inches (~8.98 sq ft) Popular 16:9 TV Dimensions Reference
Planning furniture placement or wall mounting? Here are the exact physical screen dimensions for standard 16:9 television sizes (excluding outer bezels and stands):
| Diagonal Size | Width (Inches / CM) | Height (Inches / CM) | Screen Area |
|---|---|---|---|
| 43 Inches | 37.5" (95.2 cm) | 21.1" (53.5 cm) | 790 sq in (0.51 sq m) |
| 50 Inches | 43.6" (110.7 cm) | 24.5" (62.3 cm) | 1,068 sq in (0.69 sq m) |
| 55 Inches | 47.9" (121.8 cm) | 27.0" (68.5 cm) | 1,293 sq in (0.83 sq m) |
| 65 Inches | 56.7" (143.9 cm) | 31.9" (80.9 cm) | 1,806 sq in (1.17 sq m) |
| 75 Inches | 65.4" (166.0 cm) | 36.8" (93.4 cm) | 2,404 sq in (1.55 sq m) |
| 85 Inches | 74.1" (188.2 cm) | 41.7" (105.8 cm) | 3,088 sq in (1.99 sq m) |
Evaluating pixel density and viewing distance
Physical size is only one factor when choosing a screen. For living rooms, optimal display size depends on seating distance—check our TV Size & Viewing Distance Calculator to match screen size to your room layout. For computer monitors and smartphone screens, calculate sharpness and pixel clarity using our PPI (Pixels Per Inch) Calculator.
If you already know your screen's pixel width and height and want to find its proportional ratio, use the Aspect Ratio Calculator.
Frequently asked questions
How big is a 55 inch TV?
A standard 55-inch 16:9 television display measures 47.9 inches (121.8 cm) wide and 27.0 inches (68.5 cm) tall, with a total surface area of approximately 8.98 square feet (0.83 sq meters). Note that physical frame bezels and stands add slightly to total dimensions.
Why are screens measured diagonally instead of by width and height?
Diagonal measurement originated during early circular cathode-ray tube (CRT) television manufacturing, where circular screen diameters were standard. The single-number diagonal specification remained standard as display technology transitioned to rectangular screens.
How do aspect ratios affect screen area?
At any given diagonal size, screens closer to a square (like 4:3 or 1:1) have significantly more total surface area than ultra-wide screens (like 21:9 or 32:9). For example, a 50-inch 4:3 display provides ~1,200 sq inches of surface area, compared to ~1,068 sq inches on a 50-inch 16:9 screen.
What aspect ratio is used by modern smartphones?
Most modern smartphones use taller aspect ratios between 19:9 and 20:9 (such as 19.5:9 on modern iPhones and Samsung Galaxy devices).