Aspect Ratio Calculator
Calculate and maintain aspect ratios for images and videos. Runs on your device — nothing is uploaded, nothing is stored.
Aspect Ratio Calculator turns a pair of pixel dimensions into a ratio, and turns a ratio plus one known side into the missing one. It's for the everyday jobs where a design, a video or a thumbnail has to keep its proportions: working out what 1920 × 1080 reduces to, or how tall a 16:9 banner is if it must be 1280 pixels wide.
The first tab takes a width and a height, reduces them to the simplest ratio (1920 × 1080 becomes 16:9) and shows the decimal value alongside. Below it sit eight one-click presets — 16:9, 4:3, 1:1, 21:9, 3:2, 9:16, 4:5 and 2.39:1 — that fill in the dimensions for you. The second tab goes the other way: enter a ratio, say whether you know the width or the height, give that value in pixels, and it returns the other side.
It's plain arithmetic on the numbers you type, so there is no file to upload and nothing leaves your browser. It calculates dimensions only; it does not resize or crop an image.
- Enter a width and height to see the simplified ratio and its decimal value, or tap a preset.
- Switch to the Ratio to Scale tab to work from a known ratio.
- Choose whether you know the width or the height and enter it in pixels.
- Read off the missing dimension and apply it in your design, editor or video tool.