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Aspect Ratio & Screen Size Calculator

Pick a common aspect ratio (16:9, 4:3, 21:9, 9:16 …) or type any custom W:H, then enter any one of width, height or diagonal — the other two pop out instantly. Handy for working out the real width and height of a TV / monitor from its diagonal in inches, or for cropping a design from one given side. When the unit is pixels you also get the total resolution in megapixels.

Custom W : H
:

Ratio preview

Width W Result
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Height H Result
—
Diagonal D Result
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Ratio (simplified)
—

Use "diagonal" for monitor / phone / TV sizes (usually quoted in inches); use "width" or "height" for design crops and image planning.

Formula

W : H = w : h · D² = W² + H² · H = D / √((W/H)² + 1)

Formula

W : H = w : h // ratio is preserved H = D / √((W/H)² + 1) // height from a diagonal W = (W/H) × H // width from height D² = W² + H² // Pythagoras (diagonal) Total pixels = W × H (when unit is px)

Frequently asked

What are the real width and height of a 27-inch 16:9 monitor?

Plug into the formula: width = 27 × 16/√(16²+9²) = 27 × 16/√337 ≈ 23.53 in (≈ 59.77 cm); height = 27 × 9/√337 ≈ 13.24 in (≈ 33.62 cm). Try it above by selecting 16:9, entering 27 and choosing inches. Note this is the viewable area — it excludes the bezel.

Why do 1920×1080, 2560×1440 and 3840×2160 all simplify to 16:9?

Type any of those into the custom W:H fields above — the "Ratio (simplified)" row will read 16:9. Each pair is a multiple of 16:9: 1920÷16 = 1080÷9 = 120, 2560÷16 = 1440÷9 = 160, and 3840÷16 = 2160÷9 = 240. The simplification uses the greatest common divisor (gcd) under the hood.

I'm shooting a 9:16 vertical video for TikTok / Reels — what is the 1080p resolution?

Pick the 9:16 preset, set "I know" to "Width W", type 1080 and choose pixels. You'll get W = 1080 px, H = 1920 px, diagonal ≈ 2202 px and ≈ 2.07 MP — essentially 1080p turned sideways, which is the standard upload size for TikTok, Instagram Reels and YouTube Shorts.

Which has more viewable area — a 34" 21:9 UltraWide or a 32" 16:9 monitor?

A 34" 21:9 gives width ≈ 31.36 in, height ≈ 13.44 in and area ≈ 421.6 in². A 32" 16:9 gives width ≈ 27.89 in, height ≈ 15.69 in and area ≈ 437.6 in² — slightly larger in total area (~4 % more), even though the UltraWide is 3.5 in wider for multitasking and timeline-heavy work. You can verify both above with the diagonal mode.

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