The Aspect Ratio Calculator does two related jobs: it reduces any width and height to a clean ratio in lowest terms (like 16:9 or 4:3), and it resizes a dimension while keeping that ratio locked so images and videos are never stretched. It is essential for video editing, photography, thumbnails, responsive web design and print layouts.
How it works
To find the ratio, the tool divides the width and height by their greatest common divisor (GCD). So 1920 and 1080 both divide by 120, giving 16:9. It also shows the ratio as a single decimal (width ÷ height).
To resize proportionally, it solves for the missing dimension using the original ratio:
new height = new width ÷ (original width ÷ original height)
Enter a new target width and the matching height is calculated instantly, so the proportions stay identical and nothing is distorted.
Example
A 1920×1080 frame reduces to 16:9 (decimal 1.778). Resizing the width to 1280 keeps the ratio:
new height = 1280 ÷ (1920 ÷ 1080) = 1280 ÷ 1.778 = 720.
| Width | Height | Ratio |
|---|---|---|
| 1920 | 1080 | 16:9 |
| 1280 | 720 | 16:9 |
| 1280 | 1024 | 5:4 |
| 1080 | 1080 | 1:1 |
Every calculation runs locally in your browser and nothing is sent to a server.