Image, video and display dimensions tool
Aspect Ratio Calculator
Simplify width and height to an aspect ratio, resize dimensions without distortion, solve a missing side from a target ratio, or find the largest centered crop.
Aspect ratio formulas
An aspect ratio compares width with height: aspect ratio = width ÷ height. Integer dimensions are reduced by dividing both sides by their greatest common divisor.
To resize from a new width: new height = new width × original height ÷ original width. To resize from a new height: new width = new height × original width ÷ original height.
For a centered crop, the calculator keeps the full height and trims width when the source is wider than the target ratio. Otherwise, it keeps the full width and trims height. Crop dimensions are rounded to whole pixels.
Checked examples
| Task | Inputs | Checked result |
|---|---|---|
| Simplify and resize | 1920 × 1080; new width 1280 | 16:9; 1280 × 720; 66.6667% scale |
| Build from ratio | 4:3; width 1200 | 1200 × 900 |
| Centered crop | 4000 × 3000 to 16:9 | 4000 × 2250; 75% retained; 3,000,000 pixels removed |
Common aspect ratios
| Ratio | Typical use | Example dimensions |
|---|---|---|
| 1:1 | Square images | 1080 × 1080 |
| 4:3 | Traditional displays and photos | 1600 × 1200 |
| 3:2 | Many cameras and prints | 6000 × 4000 |
| 16:9 | HD and UHD video | 1920 × 1080 |
| 9:16 | Vertical video | 1080 × 1920 |
| 21:9 | Ultrawide display format | 2560 × 1080 is approximately 21:9 |
Limits and practical checks
- Keep every dimension in the same unit. Pixel dimensions are counts, while inches and centimeters describe physical size.
- Aspect ratio alone does not determine resolution, print quality, file size or pixel density.
- A centered crop is only a geometric suggestion. Move the crop when the subject is not centered.
- Whole-pixel rounding can make the displayed crop ratio differ very slightly from the mathematical target.
- The calculator accepts positive values up to 1,000,000,000 and requires whole pixels for source and crop dimensions.