Aspect Ratio Calculator

The Aspect Ratio Calculator lives at krumzi.com/tools/aspect-ratio-calculator. It's free, there's no signup, and it does three jobs from one page: work out a ratio, resize a set of dimensions, or crop an image to every social platform in one go.

Calculate mode

Type a Width and Height and the tool shows the simplified ratio (for example 1920 by 1080 becomes 16:9), the decimal value, and whether the shape is landscape, portrait, or square. If the numbers match a common named ratio, it tells you which one. A live preview box updates as you type so you can see the shape, not just the math.

Below the inputs is a row of platform presets: Instagram square, portrait, landscape, Story and Reel, TikTok, YouTube video, Shorts and thumbnail, Facebook post, story and cover, LinkedIn post and cover, X image post and header, Pinterest standard and tall pins, and Snapchat. Click one to load its exact pixel size into the calculator.

Resize mode

Enter your original width and height, then fill in either the New width or the New height. The other side is calculated for you so the proportions stay intact and nothing gets stretched. Tick Round to whole pixels if you want clean integers for an export dialog. This is the mode to use when a client hands you a 3000 by 2000 photo and you need to know how tall it should be at 1200 wide.

Resize image mode

Drop an image (up to 20 MB) and the tool renders a preview tile for every platform preset at once. Each tile uses a centered smart crop. If the automatic framing cuts off the wrong part, drag inside a tile to reposition the crop for that platform. Download tiles one at a time, or hit Download all sizes (ZIP) to get every platform size as PNG files in a single archive.

Everything in this mode happens in your browser. Your image is never uploaded to a server.

Prefilled calculators

The main page also links out to prefilled versions for the ratios and platforms people search for most, such as 16:9, 9:16, 1:1, 4:5, Instagram Story, TikTok, YouTube thumbnail, LinkedIn, and Pinterest. Each one opens with the numbers already loaded and shows a quick dimensions table above the fold, so you get the answer before you scroll.

When to use it

• You have one hero image and need it sized for five platforms before a launch.

• You're briefing a designer and want exact pixel dimensions instead of "make it Instagram-shaped".

• You need to check whether a video file is actually 16:9 before you upload it.

If you'd rather have the design made for you in the right size from the start, the full Krumzi app generates images, carousels, and videos at platform presets and lets you resize any design afterwards.