Screen Size Chart: TV, Monitor and Laptop Sizes

A screen's width and height come from its diagonal and its aspect ratio. To find the width, multiply the diagonal by the first number in the ratio, then divide by the square root of the first number squared plus the second number squared. The height works the same way, with the second number in place of the first.

Take a 55-inch 16:9 TV. Its screen is 121.8 cm (47.9 inches)47.9 inches (121.8 cm) wide and 68.5 cm (27.0 inches)27.0 inches (68.5 cm) tall, or about 8339 cm² (1293 in²)1293 in² (8339 cm²) of picture.

The diagonal measures only the lit screen, corner to corner. It leaves out the frame and the stand, so the TV itself is bigger than its screen. Spec sheets list the size with and without the stand, and that's the number to use for a wall or a cabinet.

Area is width times height, so two screens with the same diagonal can cover different areas when their shapes differ. A 15.6-inch 16:9 laptop screen is 34.5 × 19.4 cm (13.6 × 7.6 inches)13.6 × 7.6 inches (34.5 × 19.4 cm), for 671 cm² (104 in²)104 in² (671 cm²). The same diagonal in 16:10 is 33.6 × 21.0 cm (13.2 × 8.3 inches)13.2 × 8.3 inches (33.6 × 21.0 cm), for 706 cm² (109 in²)109 in² (706 cm²).

The 16:10 screen is a little narrower but taller, and that extra height adds about 5% more area overall.

A bigger diagonal doesn't always mean more area. A 34-inch 21:9 ultrawide is 79.4 × 34.0 cm (31.3 × 13.4 inches)31.3 × 13.4 inches (79.4 × 34.0 cm), and a 32-inch 16:9 monitor is 70.8 × 39.8 cm (27.9 × 15.7 inches)27.9 × 15.7 inches (70.8 × 39.8 cm).

The ultrawide has a longer diagonal and is 8.5 cm (3.4 in)3.4 in (8.5 cm) wider, but the 32-inch 16:9 has about 5% more area.

If the desk sets the limit, compare widths. If you want the most screen surface, compare areas. The diagonal alone answers neither question.

Use the width column for wall space and cabinets. Measure first, then pick the largest size that fits with a little room to spare, since the frame and stand add width. A 65-inch screen alone is 143.9 cm (56.7 inches)56.7 inches (143.9 cm) wide, so measure the wall or cabinet at least that wide before you commit.

Stands can be wider than the screen. Check the spec sheet for the width with the stand before you buy furniture.

For seat distance, use the Viewing Distance tool. It shows the 40-degree and 30-degree seats for any TV size. A 65-inch TV fills a 40-degree view from 2.0 m (6.5 ft)6.5 ft (2.0 m), and a 30-degree view from 2.7 m (8.8 ft)8.8 ft (2.7 m).

Phone and tablet screens don't share one shape. Ratios change from model to model, so each phone and tablet row uses a common resolution and names it. Your device may differ a little from its row.

Phone makers often measure the diagonal as a standard rectangle that encloses the rounded corners. The viewable area is a little smaller than that rectangle, so the usable screen can come in under the listed number.