How to resize an image by percentage
Upload the image and drag the Scale slider. 50 percent halves the width and height, 25 percent makes each side a quarter of its size, and anything above 100 percent enlarges the image. The slider runs from 5 to 200 percent. The new pixel dimensions and file size appear next to the originals after each change.
Because both sides are scaled by the same amount, the aspect ratio never changes, and nothing is cropped or stretched.
How percentage affects file size
Scaling is applied to each side, so the pixel count drops faster than the percentage suggests. At 50 percent you keep only a quarter of the pixels. At 70 percent you keep about half. The file size usually follows the pixel count, which makes percentage resizing a quick way to make photos lighter for email or the web.
If you need a precise file size rather than a rough reduction, use one of the Compress Image to N KB tools after resizing.
When to use percentage instead of pixels
Percentage is handy when the exact size doesn't matter, such as shrinking a batch of camera photos to something more manageable, or making a screenshot half as big for a document. Use pixels when a platform asks for a specific width. For many images at once, the Bulk Image Resizer applies the same percentage to up to 20 files.
Choosing a percentage
For photos from a modern phone, 25 to 50 percent usually leaves plenty of resolution for screens, email and social media. For screenshots taken on a high-density laptop or phone screen, 50 percent brings them back to the size they appeared on screen. For images that are already small, stay near 100 percent or leave them as they are.