Aspect Ratio Calculator

An aspect ratio describes the proportional relationship between the width and height of an image or video. It is written as two numbers separated by a colon, such as 16:9 or 4:3. Aspect ratio matters because different platforms (YouTube, Instagram, TikTok) require specific ratios for optimal display. Using the wrong ratio causes letterboxing, pillarboxing, or cropping that can cut off important content.

Standard YouTube videos use a 16:9 aspect ratio with recommended resolutions of 1920x1080 (Full HD), 2560x1440 (2K), or 3840x2160 (4K). YouTube Shorts use 9:16 (vertical), typically 1080x1920 pixels. YouTube thumbnails are also 16:9 at 1280x720 pixels. The platform automatically adds black bars if your video does not match 16:9.

Instagram supports multiple aspect ratios: 1:1 (1080x1080) for square feed posts, 4:5 (1080x1350) for portrait feed posts which take up the most screen space, 9:16 (1080x1920) for Stories and Reels, and 1.91:1 (1080x566) for landscape posts. For maximum engagement, use 4:5 portrait for feed posts and 9:16 for Stories and Reels.

To resize without distortion, you must maintain the original aspect ratio. Calculate the ratio from the original dimensions (e.g., 1920x1080 simplifies to 16:9), then use this ratio for the new size. For example, to make a 16:9 image 800px wide: 800 / 16 * 9 = 450, so the new dimensions are 800x450. Our resize calculator above does this automatically.

16:9 is the standard widescreen ratio used by most monitors, TVs, and streaming platforms. 4:3 is the classic "standard" ratio from older TVs and monitors, still used for some presentations and documents. 21:9 is ultrawide, used for cinematic films and ultrawide monitors. In pixels: 16:9 = 1920x1080, 4:3 = 1440x1080, 21:9 = 2560x1080. The wider the first number relative to the second, the more panoramic the image.