How to Resize an Image Online
Updated · 4 min read
Resizing changes the number of pixels in an image, its width and height. It’s how you make a photo fit a website layout, a social media post or an application form that asks for exact dimensions.
How to resize an image
- Open the image resizer and select your image.
- Choose Pixels to type an exact width and height, or Percentage to scale it, for example to 50%.
- Leave “Keep aspect ratio” on so the image isn’t stretched.
- Pick an output format, select Resize image and download the result.
Aspect ratio: avoid stretched photos
The aspect ratio is the relationship between width and height. A typical phone photo is 4:3, for example 4000 × 3000 pixels. If you resize it to 1200 wide, the height must be 900 to keep the same shape. Forcing it into 1200 × 1200 squashes everything horizontally.
When a site needs a different shape, such as a square profile picture, crop the photo to that shape first in your phone’s or computer’s photo editor, then resize.
Making images smaller vs. larger
Reducing an image is safe: detail is condensed, and the result looks sharp. Enlarging can’t add detail that the camera didn’t capture, so upscaled images look soft. If you need a large image, start from the highest-resolution original you have.
Pixels, centimetres and DPI
Some forms give sizes in centimetres or inches, such as 3.5 × 4.5 cm for a passport photo. To convert, multiply by the print resolution: at 300 DPI, 1 inch is 300 pixels and 1 cm is about 118 pixels. So 3.5 × 4.5 cm at 300 DPI is about 413 × 531 pixels. Check whether the form specifies a DPI; if not, many use 200–300.
Resizing to reduce file size
Fewer pixels means a smaller file. Halving both dimensions typically cuts the file size by about 75%. If your goal is a specific size in KB, it’s easier to use Compress Image to 100KB or 50KB, which adjust dimensions automatically.