Screen Size Comparison Calculator
Compare two TVs, monitors or phones with different diagonals and aspect ratios: width, height, area, how much bigger one really is, and the 16:9 size with the same height.
How it works
width = diagonal × w ÷ √(w² + h²) · height = diagonal × h ÷ √(w² + h²) · area ratio = (W₂ × H₂) ÷ (W₁ × H₁)
A screen’s diagonal alone is misleading when the aspect ratios differ: a 34-inch 21:9 ultrawide is much wider than a 27-inch 16:9 monitor but only about as tall. Splitting each diagonal into width and height with the Pythagorean theorem gives the real dimensions, and the ratio of the areas shows how much more picture you get. The last row converts screen 2’s height into the 16:9 diagonal that would be equally tall — handy for comparing ultrawides, TVs and laptop panels.
Worked example
27″ 16:9: width = 27 × 16 ÷ 18.358 = 23.53″ (59.8 cm), height 13.24″ (33.6 cm). 34″ 21:9: width = 34 × 21 ÷ 22.847 = 31.25″ (79.4 cm), height 13.39″ (34.0 cm). Area ratio = 2,700 cm² ÷ 2,010 cm² = 1.34×, so the ultrawide has 34.4% more area, is 19.6 cm wider and only 0.4 cm taller — the same height as a 27.3″ 16:9 screen.
Sources: RTINGS — TV size and viewing distance · Display size (Wikipedia)
Frequently asked questions
How do I compare screen sizes with different aspect ratios?
Convert each diagonal to width and height (width = diagonal × w ÷ √(w² + h²)), then compare the areas. Diagonals alone only compare fairly when the aspect ratio is the same.
How much bigger is a 65-inch TV than a 55-inch TV?
Both are 16:9, so area scales with the square of the diagonal: (65 ÷ 55)² = 1.40, about 40% more screen area.
Is a 34-inch ultrawide bigger than a 27-inch monitor?
It has about 34% more area and is roughly 20 cm wider, but it is almost exactly as tall as a 27-inch 16:9 monitor.
Which aspect ratio is 21:9?
Marketing name for ultrawide panels; real resolutions are 2560 × 1080 (64:27) or 3440 × 1440 (43:18), both close to 2.37 : 1. The small difference barely changes the size.
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This calculator is for educational purposes. Double-check important results before acting on them.