Aspect Ratio Calculator

Use it when your task matches one of these common needs: Simplify image, video, thumbnail, and screenshot dimensions. Resize a design to a new width while preserving height proportion. It works best when you already know the original width and height, plus either the new width or the new height when you are resizing.

In plain language: The calculator scales decimal inputs to whole-number precision, divides width and height by their greatest common divisor to simplify the ratio, then uses width / height to calculate the missing scaled dimension. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.

Width: the horizontal size of the image, video, screen, card, or design. Height: the vertical size of the same item, using the same unit as width. Simplified ratio: the width and height divided by their greatest common divisor, such as 1920 x 1080 becoming 16:9. Decimal: width divided by height, useful for comparing whether two sizes have the same shape. Scaled size: the matching width or height that keeps the original shape when one dimension changes.

Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.

Aspect ratio preserves shape, not subject framing. Use exact upload specs for platforms, product images, video editors, and print jobs, and remember that rounding a scaled dimension can cause a one-pixel difference. Check whether the job needs resizing, cropping, padding, or a platform-specific preset because keeping the same ratio does not decide what part of the image stays visible.

An aspect ratio is the relationship between width and height. A 16:9 image can be 1920 x 1080, 1280 x 720, or 3840 x 2160 because each size keeps the same width-to-height shape.

Enter 1920 width, 1080 height, choose Scale by width, and enter 1280 as the new width. The matching height is 720, so the scaled size is 1280 x 720.

Some ratios produce fractional pixels after scaling. The calculator shows readable dimensions, but a platform or editor may round up or down differently, so check the final export size before uploading.

No. Resizing changes the dimensions while keeping the whole image. Cropping cuts away part of the image to fit a different shape. If a platform requires a new ratio, you may need crop or padding instead of only resizing.

No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.