A PRACTICAL IMAGE TOOL
Aspect ratio calculator.
To calculate an aspect ratio, divide the width and height by their greatest common divisor. For 1920 × 1080, both divide by 120, giving 16:9.
Find matching dimensions or crop an image to your target shape. Your image stays in this browser.
Find the ratio
Enter your pixel dimensions. Whole-number dimensions reduce to an exact ratio.
Match a ratio
Set one dimension to find the other without stretching.
Matching height: 1080 px
Matching width: enter a height
Calculated values may have fractional pixels. Round to whole pixels when exporting a raster image.
Frame your image
Choose an image or drop it below. Drag the frame to position your crop; arrow keys move it too.
or drop a file here
No upload. The image never leaves your device; nothing is saved by this site.
A useful shape,
not just a number.
How to calculate an aspect ratio
- Enter the width and height in pixels.
- Divide both dimensions by their greatest common divisor to get the reduced ratio.
- To resize without stretching, choose a target ratio and enter one dimension to calculate the other.
For example, 800 × 600 reduces to 4:3. To keep 16:9 at 1600 pixels wide, the matching height is 1600 × 9 ÷ 16 = 900 pixels. Cropping to a different shape removes pixels from the edges; scaling to a different shape distorts the image.
Common aspect ratios
These are common examples, not mandatory specifications. Platform display rules change; check the current upload requirements before publishing.
| Ratio | Example size | Common use |
|---|---|---|
| 16:9 | 1920 × 1080 | Widescreen video, YouTube landscape |
| 4:3 | 1600 × 1200 | Classic photos and displays |
| 1:1 | 1080 × 1080 | Square Instagram posts |
| 9:16 | 1080 × 1920 | Vertical video, TikTok and Stories |
| 21:9 | 2560 × 1080 | Ultrawide displays |
| 3:2 | 1800 × 1200 | Photography |
| 5:4 | 1500 × 1200 | Common 8 × 10 inch print shape |
Print dimensions in pixels depend on your chosen pixels-per-inch setting; a ratio alone does not set print resolution.
Questions, answered.
How do I calculate the aspect ratio from pixel dimensions?
Divide width and height by their greatest common divisor. 1024 × 768 becomes 4:3.
How do I resize an image to 16:9?
Multiply the width by 9/16 to find the height. A 1280-pixel width needs a 720-pixel height. If the original ratio differs, crop instead of stretching.
What is a 9:16 portrait ratio?
It is 16:9 turned upright. A 1080-pixel width at 9:16 gives a 1920-pixel height.
Should I crop or resize an image?
Resize when the original and target ratios match. Crop when they differ and you need an exact frame; cropping removes edges instead of stretching the picture.