Aspect Ratio Calculator

Instructions

1. Pick a common dimension — choose one of the presets from the "Common Dimensions" menu above and the width, height, and ratio fill in for you.
2. Or enter your own — choose "Custom" to reveal the Aspect Ratio Width and Aspect Ratio Height fields, then set the ratio you want to hold.
3. Type a width or a height — the other dimension recalculates to keep the selected aspect ratio. There is no submit button; the result and the shape preview update as you type.

Everything runs in your browser. Nothing you enter or upload is sent to a server.

Aspect Ratio Dimension Calculator

Enter common image dimensions or custom dimensions to calculate the aspect ratio.

This calculator lets you input either a width or a height, select a common or custom aspect ratio, and then calculate the corresponding dimension to maintain the selected aspect ratio. Enter a value, select the aspect ratio, and the result updates automatically.

The ratio is reported as a decimal — 1920 × 1080 reads as 1.78, not 16:9. That is the same number, expressed as width divided by height, and it is the form you want when you are feeding a value into CSS, a video encoder, or a design tool that asks for a single scalar. The shaded box beside the fields is drawn at the ratio you have selected, so you can see the shape rather than infer it from two numbers.

Image Upload Aspect Ratio Calculator

Upload an image to get its aspect ratio.

The image upload aspect ratio calculator allows you to upload an image to get its aspect ratio. This is useful for quickly determining the aspect ratio of existing images without manually measuring their dimensions. The image is read locally and previewed alongside its measured width, height, and ratio — it is never uploaded anywhere.

Common Aspect Ratios

Need help remembering that specific image aspect ratio? Here's a list of the most common social images and their shapes.

Every ratio in that table is reachable from the Common Dimensions menu, which carries a preset for each shape — 1:1, 1.48:1, 2:3, 3:2, 3:1, 4:3, 4:5, 16:9, 9:16, 21:9, and 6:1 — at the pixel sizes those platforms actually use. Platforms revise their recommended sizes from time to time; the ratio is the durable part, which is why it is what this table lists.

Who this is for

The aspect ratio calculator is useful for designers, developers, and content creators who need to maintain specific or custom aspect ratios when resizing images or videos. Common aspect ratios like 16:9, 4:3, 1:1, 3:2, and 21:9 are supported. This tool ensures that your media maintains its proportions regardless of changes in dimensions.

The practical case is usually the same one: you have a target shape and one fixed dimension — a container width, a maximum upload height — and you need the other number without doing the arithmetic by hand or eyeballing a crop. Set the ratio, type the dimension you're locked to, and read off the one you need.