Resizing an image or video while keeping proportions intact means solving a simple ratio — but doing that math by hand for every crop or export is tedious. This tool does it instantly.
What Is the Aspect Ratio Calculator?
Enter a width and height and it simplifies the ratio (like 1920×1080 → 16:9) and shows the decimal equivalent. Then enter a target width or height and it calculates the matching dimension to keep the same proportions.
How to Use It
- Open the tool at /tools/aspect-ratio-calculator.
- Enter your source width and height, or pick a common preset (16:9, 4:3, 1:1, etc.).
- Enter a target width to get the matching height, or a target height to get the matching width.
- Use the live preview box to sanity-check the shape visually.
Key Features
- Automatic ratio simplification using the Euclidean GCD algorithm.
- Bidirectional calculation — solve for height from width, or width from height.
- Six common presets for video, photo, and screen ratios.
- Visual proportion preview box.
When to Use This Tool
- Cropping or resizing images/video without distorting them.
- Planning a responsive layout that needs to preserve a specific ratio.
- Checking whether a resolution matches a named standard like 21:9 ultrawide or 9:16 vertical video.
Try It Now
Open Aspect Ratio Calculator directly, or press ⌘K and type the tool name from anywhere on the site.
Part of the CSS Tools collection on WebdevToolbox — free, browser-based developer tools with no login required.