Calculate dimensions while maintaining aspect ratio. Perfect for resizing images, videos, and responsive design.
Enter either width or height, and the other dimension will be calculated automatically.
Enter your original width and height first, then type either a new width or a new height. The missing dimension is computed from the original ratio and rounded to the nearest whole pixel. If you fill in both fields, the second value you typed wins.
Both dimensions are divided by their greatest common divisor. That is why 1920 by 1080 displays as 16:9 and 1080 by 1080 displays as 1:1, even though the pixel counts are different.
Clicking a preset such as 16:9 or 9:16 fills the original dimensions at a 100x scale (1600 by 900 for 16:9) and clears the new dimension fields, so you can immediately solve for the size you need.
The list only shows well-known resolutions (Full HD, 2K, 4K, 8K, Instagram 1080 by 1080, ultrawide 2560 by 1080, and others) whose ratio matches yours within about one percent. Unusual ratios match nothing and show a "No common resolutions" note instead.
No. Every calculation, from the greatest common divisor math to the resolution matching, runs locally on this page. No pixel dimensions leave your device.