What Is Image Aspect Ratio?

Aspect ratio is the relationship between an image's width and its height, written as two numbers separated by a colon. It describes shape, not size: 1600 by 900 and 1280 by 720 are different sizes but the same 16:9 shape.

Working it out

Divide both dimensions by their greatest common divisor. For 1920 by 1080 that divisor is 120, giving 16:9. For 4032 by 3024 it is 1008, giving 4:3. Some ratios do not reduce to friendly numbers, which is why 1366 by 768 is usually described as approximately 16:9 rather than exactly.

Why it matters more than resolution

When you place an image into a container with a different shape, something has to give. Either the image is cropped, letterboxed with bars, or stretched. Stretching is the only genuinely unacceptable option, and it is what happens when width and height are set independently without a proportional lock.

Ratios you will meet

• 16:9 for video, presentations and most modern displays.
• 1:1 for square social posts and profile images.
• 4:5 for portrait feed posts on Instagram.
• 9:16 for vertical stories and short-form video.
• 3:2 for most interchangeable-lens camera sensors.
• 1.91:1 for link preview cards, which is where 1200 by 630 comes from.

Shooting with cropping in mind

If a photo will be published in several ratios, leave space around the subject. A tightly framed shot cannot survive a crop to 1:1 or 9:16 without cutting into what matters. Photographers call this breathing room, and it costs nothing at capture time.