A PRACTICAL IMAGE TOOL
Aspect ratio crop calculator.
Aspect ratio crop starts with the ratio itself: 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.
Frequently asked questions
How do I calculate an aspect ratio?
Divide the width and the height by their greatest common divisor. For 1920 × 1080, both numbers divide by 120, which gives 16:9.
How do I crop an image to an aspect ratio?
Choose a crop ratio, select a PNG or JPEG image, drag the frame (or use the arrow keys) to position it, then download the crop as PNG or JPEG.
How do I find the height that keeps my ratio?
Pick a target ratio and enter one dimension. The matching dimension is calculated for you. It can contain fractional pixels, so round to whole pixels when you export a raster image.
Is my image uploaded anywhere?
No. The image is decoded and exported in your browser, so no image data is sent to a server.
Which image formats can I use?
Choose a PNG or JPEG image, and download the result as PNG or JPEG.
Are the platform sizes official upload requirements?
No. Dimensions shown for social platforms and devices are common examples, not current platform upload specifications. Confirm them with each service when you publish.
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.