Aspect Ratio Calculator

An aspect ratio is the relationship between an image's width and its height, written as width:height. A 16:9 frame is 16 units wide for every 9 units tall. The ratio describes the shape of the frame, not its size. A tiny 160×90 thumbnail and a 3840×2160 4K export are both 16:9 because they share the exact same shape.

Aspect ratio and resolution are not the same thing. Resolution is the raw pixel count, like 1920×1080. Aspect ratio is the shape those pixels form, like 16:9. Two images can share a ratio and have completely different resolutions. More resolution means more detail, but the shape stays put.

Ratios come in three orientations. When the width is larger, the frame is landscape, like 16:9 video. When the height is larger, it is portrait, like 9:16 Reels. When the two match, it is square, like 1:1. Flip a ratio and you flip the orientation: 16:9 landscape becomes 9:16 portrait.

To find the aspect ratio of any image, divide the width by the height. 1920 ÷ 1080 gives 1.78, which is 16:9 written in whole numbers. To reach that clean whole-number form, divide both sides by their greatest common divisor. The greatest common divisor of 1920 and 1080 is 120, so 1920:1080 reduces to 16:9. The calculator above does this the instant you type a width and a height, but the math is simple enough to run by hand.

The most common real task is not naming a ratio, it is finding a missing side. Say your video needs to be 16:9 and you want it 1280 pixels wide. How tall should it be?

Set it up as a proportion: width ÷ height equals 16 ÷ 9. Rearrange to solve for the height: height = width × 9 ÷ 16. Plug in your width: 1280 × 9 ÷ 16 = 720. So a 16:9 frame that is 1280 wide is 720 tall. That is exactly why 1280×720 is a standard HD size.

The same move works in reverse. To find the width when you already know the height, use width = height × 16 ÷ 9. A 16:9 frame that is 1080 tall is 1080 × 16 ÷ 9 = 1920 wide, which is Full HD. Portrait works identically: a 9:16 Story that is 1080 wide is 1080 × 16 ÷ 9 = 1920 tall, the 1080×1920 every vertical platform asks for. Swap in any ratio's two numbers and the formula holds for every shape.

You do not need to memorize ratios. When someone hands you a size like 1080×1350 and asks what ratio it is, divide: 1080 ÷ 1350 = 0.8. Then simplify 1080:1350 by their greatest common divisor, which is 270, and you get 4:5. Any width and height reduces to a named ratio this way, and the calculator labels the closest standard match for you automatically.

There are two ways to change an image's size. Resizing scales the whole image and keeps every pixel, which only stays sharp when the new size shares the original ratio. Cropping cuts pixels away to reach a new ratio, which is what happens when you take a 16:9 photo to a 1:1 square. When your source and target ratios do not match, something has to go, so decide what to keep before you export instead of letting a platform decide for you.

Match the ratio your destination expects and nothing gets cropped, squashed, or letterboxed. Miss it and the platform makes the call for you, usually by cutting off the part of your image you cared about most. Pick a ratio below to open a calculator that is already set up, or drop an image in and download every social size at once.