Aspect Ratio Calculator
Calculate width, height, or aspect ratio for video, images and screens — keep 16:9, 4:3, 21:9 and more perfectly proportional.
Aspect ratio
Dimensions
Enter the width or the height and the other one is calculated from the ratio.
1920 × 108016:9About this tool
This aspect ratio calculator keeps your width and height in perfect proportion. Pick a ratio such as 16:9 and type a width, and it instantly works out the matching height (and the other way around). You can also type any two dimensions and read back the simplified ratio — for example 1920 × 1080 reduces to 16:9 and 1280 × 1024 to 5:4. Presets cover the most common screen, photo and video ratios, a live preview draws the shape, and every result can be copied with one click. It all runs in your browser, so it is instant and works offline once loaded.
How to use
- 1 Pick a preset ratio (16:9, 4:3, 21:9, 1:1, 3:2, 9:16) or type your own ratio.
- 2 Enter a known width or height; the matching dimension is filled in for you.
- 3 Or type any two dimensions to read their simplified ratio below.
- 4 Copy the calculated size or simplified ratio with the copy buttons.
How it works
An aspect ratio is just the proportion of width to height, written W:H. To find a missing dimension the calculator keeps that proportion constant: height = width × ratioH ÷ ratioW, and width = height × ratioW ÷ ratioH. So a 16:9 frame that is 1920 wide must be 1920 × 9 ÷ 16 = 1080 tall. To turn two pixel dimensions back into a clean ratio, it divides both numbers by their greatest common divisor (GCD); for 1920 and 1080 the GCD is 120, giving 16:9. Because the maths is pure proportion, the same logic scales any video, photo, screen or canvas without distortion.
Frequently asked questions
What aspect ratio is 1920 × 1080?
1920 × 1080 (Full HD) is a 16:9 ratio. Dividing both numbers by their greatest common divisor, 120, gives 16:9 — the standard for most TVs, monitors, YouTube and streaming video.
How do I find the height for a given width?
Choose your ratio (for example 16:9) and type the width into the width field. The height is calculated as width × ratioH ÷ ratioW. A width of 1920 at 16:9 gives 1080; you can also work backwards by typing a height to get the width.
What are the most common aspect ratios?
16:9 is the standard for video and modern screens, 4:3 is classic TV and many photos, 21:9 is ultrawide and cinema, 1:1 is square (social posts), 3:2 is common for cameras and prints, and 9:16 is vertical for phones, Reels, Shorts and TikTok.
Does resizing to a different aspect ratio distort the image?
Yes — if you change to a ratio that does not match the original, the picture is stretched or squashed unless you crop or add letterbox bars. Use this calculator to find dimensions that keep the same ratio so the image stays sharp and undistorted.
Related tools and uses
An aspect ratio calculator is handy for video editors, photographers, web designers and anyone preparing thumbnails, banners or social posts. Pair it with the percentage calculator for scaling, the color converter for matching palettes, and the comparison tool for sizing up dimensions side by side.