← Spark & Whetstone · Twenty-Four a Second
The Screen Size Table
A 65-inch screen sounds a little bigger than a 55-inch one. The number is the diagonal, though, and the picture is an area. Type two screens and see the difference in picture.
Screen one
Screen two
Side by side
Drawn to the same scale: screen one is the shaded rectangle, screen two the dashed outline.
The arithmetic
A 16:9 screen is 16 units wide and 9 high, and by Pythagoras its diagonal is √(16² + 9²), about 18.36 units. So a 55-inch 16:9 screen is 55 × 16 ÷ 18.36, about 47.9 inches wide, and 27.0 inches high. Area grows with the square of the diagonal: 65 inches is 18% more diagonal than 55, but (65 ÷ 55)², about 40% more picture.
Shape matters too. At the same diagonal a squarer screen holds more area, so a 4:3 screen has about 12% more area than a 16:9 screen with the same number on the box, though a widescreen film shown on it gets black bars.
Nothing on this page is stored or sent.