Screen Size Converter: Calculate Width, Height, and Area from Diagonal Size
Buying a new monitor or TV? The diagonal size alone does not tell you how wide or tall the screen actually is — that depends on the aspect ratio. Our converter calculates exact width, height, and screen area in both inches and centimetres for any diagonal size and aspect ratio combination.
The aspect ratio comparison table shows you exactly how different aspect ratios compare at the same diagonal — essential knowledge when choosing between 16:9, 21:9 ultrawide, or 32:9 super ultrawide displays.
Screen size calculation formula:
Aspect Ratio Quick Reference
16:9 (1.78:1) - Standard widescreen. Every modern TV, most monitors. Best for video content and gaming.
16:10 (1.6:1) - Slightly taller than 16:9. Common in laptops and pro monitors. More vertical space for documents.
21:9 (2.33:1) - Ultrawide. Great for productivity, multitasking, and cinematic games. Letterbox-free for 21:9 movies.
32:9 (3.56:1) - Super ultrawide. Replaces dual monitors. For extreme multitasking and immersive gaming.
4:3 (1.33:1) - Old TV standard. More vertical space, good for documents and older software.
Monitor vs TV Sizing Guide
Desk monitors (viewing at arm's length ~60cm):
24 inch = 53.1 x 29.9 cm (16:9) - entry level
27 inch = 59.8 x 33.6 cm (16:9) - most popular
32 inch = 70.8 x 39.8 cm (16:9) - large desktop
34 inch = 79.5 x 33.4 cm (21:9) - ultrawide
Living room TVs (viewing at 2-4m):
55 inch = 121.3 x 68.2 cm (16:9)
65 inch = 143.9 x 80.9 cm (16:9)
75 inch = 166.1 x 93.4 cm (16:9)
Practical Examples
Buying a monitor
- 1.Enter your desk space width available
- 2.Try 27 inch 16:9 - width: 23.5 inches
- 3.Compare with 34 inch 21:9 - width: 31.5 inches
- 4.Check aspect ratio comparison for your use case
Finding TV viewing distance
- 1.Enter TV diagonal (e.g. 65 inches)
- 2.Note width: 56.7 inches = 4.7 feet
- 3.Ideal distance: diagonal x 1.5 to 2.5 feet
- 4.65 inches: sit 8-13 feet away
Frequently Asked Questions
How is screen size measured?
Screen size is measured diagonally corner to corner, in inches, not including the bezel (frame). A 27-inch monitor means the diagonal of the visible screen area is 27 inches. The actual width and height depend on the aspect ratio of the screen.
How do I calculate screen width and height from diagonal?
Using the Pythagorean theorem: if the aspect ratio is W:H, Width = Diagonal x W / sqrt(W^2 + H^2), Height = Diagonal x H / sqrt(W^2 + H^2). For a 27-inch 16:9 screen: Width = 27 x 16 / sqrt(256+81) = 27 x 16 / 18.36 = 23.53 inches, Height = 27 x 9 / 18.36 = 13.24 inches.
What is the difference between 16:9 and 21:9?
Both can have the same diagonal, but 21:9 (ultrawide) is much wider and shorter than 16:9. A 27-inch 16:9 monitor is 23.53 x 13.24 inches. A 27-inch 21:9 monitor is 25.01 x 10.72 inches. The 21:9 gives more horizontal workspace but less vertical height. Total screen area is actually less on the 21:9 despite being wider.
Which aspect ratio has the most screen area?
At the same diagonal, screen area depends on aspect ratio. Closest to square ratios have more area for the same diagonal. 4:3 has more total area than 16:9 at the same diagonal. 16:9 has more area than 21:9. 21:9 has more than 32:9. However, usable area for your use case (video, productivity) is what matters more than raw area.
What is a good monitor size for work?
For productivity: 24-27 inches at 1080p or 1440p is ideal for most desks. For programming and multitasking: 27-32 inches or a 34-inch ultrawide. For video editing: 27-32 inches at 4K or a 34-inch ultrawide. For gaming: 27 inches at 1440p/165Hz is the sweet spot. Anything larger needs 4K resolution to avoid visible pixels.
How far should I sit from my TV?
Recommended viewing distance is 1.5-2.5 times the screen diagonal. For a 55-inch TV: sit 6.9-11.5 feet away. For a 65-inch TV: sit 8.1-13.5 feet away. For HDR/4K content the minimum comfortable distance is closer - about 1.0-1.5x diagonal, since higher resolution allows closer viewing without visible pixels.
What is 32:9 super ultrawide?
32:9 is an ultra-panoramic aspect ratio that is essentially two 16:9 monitors side by side. These screens (like the Samsung Odyssey Neo) are typically 49 inches diagonal, giving approximately 47.88 x 13.47 inches of usable space. They replace dual-monitor setups with a single seamless display. Popular for immersive gaming and extreme multitasking.
Why does a bigger TV have less resolution than a monitor?
Screen resolution (number of pixels) is separate from screen size. A 24-inch 1080p monitor and a 65-inch 1080p TV both have the same number of pixels (1920x1080). The TV just spreads them over a much larger area, making individual pixels visible up close. That is why TVs need 4K resolution to look sharp, while monitors can use 1080p at 24 inches.