Aspect Ratio Calculator

An aspect ratio expresses the proportional relationship between width and height as W:H. It matters because it determines the shape of the image - whether it's wide, square, or tall. When you upload to a platform that expects a specific ratio (like 16:9 for YouTube), a mismatched image gets cropped or letterboxed automatically, often in undesirable ways. Knowing the ratio before you resize or export saves time and avoids quality loss. Not sure of an existing image's dimensions? Use the Image Metadata Viewer to check its exact pixel dimensions instantly. For print, use the DPI / PPI Calculator to confirm your pixel dimensions will produce a sharp physical print at the right size.

Use the formula: new Height = (new Width ÷ old Width) × old Height. For example, scaling 1920×1080 to a width of 1280: new height = (1280 ÷ 1920) × 1080 = 720 px. The calculator above does this automatically - just lock the ratio and type a new width or height.

16:9 is a wider "widescreen" format used by modern HD televisions, YouTube videos, and most computer monitors. 4:3 is a more square "standard" format used by older televisions and monitors from before the HD era. Photos taken on many cameras are still 4:3 by default. Decimal-wise, 16:9 ≈ 1.78 while 4:3 ≈ 1.33.

Instagram supports multiple ratios depending on content type. For feed posts, 4:5 (1080×1350 px) is recommended for portrait images as it takes up the most space. Square 1:1 (1080×1080 px) works universally. Landscape posts use 1.91:1 (1080×566 px). Stories and Reels use 9:16 (1080×1920 px). Avoid going more portrait than 4:5 - Instagram will crop it automatically.

Use the "Check Ratio" tab above - enter your image's pixel width and height and it will show the simplified ratio instantly. Alternatively, divide the width by the height to get the decimal ratio (e.g. 1920÷1080 = 1.7778), then look up the nearest standard ratio. Our calculator handles the GCD simplification automatically so you always get clean numbers like 16:9 instead of 1920:1080.

Yes - this is called "constrained proportional scaling". Lock the ratio in the calculator above, then enter the new width or height and the other value is calculated for you. In photo editors, hold Shift while dragging a corner handle, or enable the "Constrain proportions" or "Lock aspect ratio" checkbox in the resize dialog. Our Photo Editor also lets you resize while maintaining the original ratio.

Common print ratios depend on the paper size. A 4×6" print is 3:2, a 5×7" print is 5:7, and an 8×10" print is 4:5. A4/Letter paper is roughly 1:√2 ≈ 0.707 (portrait). For professional printing, match the aspect ratio of your image to the print size before ordering to control exactly how the image is cropped or placed.