Aspect Ratio Calculator

Calculate missing width or height for any aspect ratio, find the ratio from dimensions, or scale any size while preserving ratio. Includes common presets and a visual preview.

16:9
HD / Widescreen
4:3
Standard / iPad
1:1
Square / Instagram
9:16
Portrait / Reel
21:9
Ultrawide
3:2
DSLR Photo
5:4
Monitor
1.91:1
Open Graph

Enter either Width or Height — the other is calculated automatically.

Common Aspect Ratios

16:9 is the universal widescreen standard — HD and 4K TVs, YouTube, Zoom, PowerPoint, and most monitors. 4:3 is the old television and monitor standard, still used by iPad screens and some cameras. 1:1 (square) is used by Instagram posts, profile pictures, and some print formats. 9:16 is portrait orientation — Instagram Reels, TikTok, YouTube Shorts. 3:2 is the standard DSLR sensor ratio (based on 35mm film). 21:9 is ultrawide cinema and gaming monitor format.

How to Calculate Aspect Ratio

Divide the width by the height, then simplify by finding the GCD (Greatest Common Divisor). For 1920×1080: GCD(1920,1080)=120, so 1920÷120=16 and 1080÷120=9, giving 16:9. To find a missing dimension: if you know the ratio is 16:9 and the width is 1280, height = 1280 × (9÷16) = 720.

Common 16:9 resolutions: 1280×720 (HD), 1920×1080 (Full HD), 2560×1440 (QHD/2K), 3840×2160 (4K UHD). Any resolution where width ÷ height = 1.777... is 16:9.
Use Mode 3 (Scale) above. Enter the original dimensions, then enter either new width or new height — the other is calculated automatically to preserve the original ratio.
Most modern smartphones use 19.5:9, 20:9, or 18:9 (roughly 2:1). Older phones used 16:9. Content shot vertically is 9:16 when rotated to landscape.

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