Aspect Ratio Calculator

The Aspect Ratio Calculator helps you maintain correct proportions when resizing images, designing video frames, cropping photos, or specifying responsive layout dimensions.

Step 1: Choose your mode: - 'Find missing dimension': enter a known aspect ratio and one dimension to calculate the other - 'Find aspect ratio': enter both width and height to get the simplified ratio - 'Resize keeping ratio': enter original dimensions and a new value for one side to scale the other proportionally

Step 2: For 'Find missing dimension', select a common preset (16:9, 4:3, 1:1, 9:16, 3:2) or enter a custom ratio by typing values into the ratio fields.

Step 3: Enter the known measurement in pixels. Other units such as inches or centimetres work too — the ratio calculation is unit-agnostic.

Step 4: Click 'Calculate'. The tool returns the missing dimension and shows a live preview box scaled to the correct proportions so you can visually confirm the shape before using the values.

Step 5: Use the comparison table to see your dimensions expressed as multiple common aspect ratios side by side — useful when preparing the same image for different social media platforms that each require different crop dimensions.

Aspect ratio is the proportional relationship between an image's or screen's width and height, expressed as two numbers separated by a colon (e.g., 16:9). Maintaining the correct ratio when resizing prevents distortion — where objects appear stretched horizontally or compressed vertically.

Different platforms and media types have their own standard ratios. Broadcast television and online video uses 16:9. Cinema often uses 2.39:1 anamorphic widescreen. Portrait smartphone video uses 9:16. Professional photography from DSLR cameras uses 3:2. Understanding these conventions helps photographers, video editors, web designers, and social media managers prepare assets correctly without trial and error.

This calculator is particularly useful when adapting a single piece of content for multiple platforms — for example, reformatting a 16:9 YouTube thumbnail for an Instagram square post (1:1) or a Pinterest vertical pin (2:3), where the crop dimensions change but the underlying image must remain undistorted.