Resizing: what it changes
Resizing changes how many pixels an image has. Make it smaller and the picture is the same, with less detail and a smaller file. Make it larger and the tool has to invent the new pixels from the old ones, which cannot add real detail, so an enlarged image looks soft. As a rule, resize down freely, and resize up only as far as you must.
Pixels, percentage or a ready-made size
- Exact pixels when a form or a platform names a size, such as 600 × 600 for a visa photo or 1080 × 1080 for a square post.
- A percentage when you simply want it smaller, for example 50% to get a quarter of the pixels.
- A preset when the size has a name. The shortcuts below cover square posts, passport photos and the common social formats.
Keep the proportions, or you will distort the picture
Every image has an aspect ratio, the relationship between its width and its height. If you change only one dimension, or both by different amounts, the picture is stretched or squashed, and faces look wrong immediately. Keep the aspect ratio locked and enter one dimension, and the other follows. If you need a shape that differs from the original, such as a square from a landscape photo, crop to that shape first rather than stretching; see crop image.
| Original | Resize to | Result |
|---|---|---|
| 4000 × 3000 (4:3) | Width 1200, ratio locked | 1200 × 900, the same picture, smaller |
| 4000 × 3000 (4:3) | 1200 × 1200, ratio unlocked | A stretched, distorted picture |
| 4000 × 3000 (4:3) | Crop to square, then 1200 × 1200 | A clean square with the sides trimmed |
Resolution and file size
Pixels are what drive file size. A 4000 × 3000 photo has 12 million pixels, and a 1200 × 900 copy has just over one million, about a ninth of the data. Resizing is the most effective way to make a file lighter, more than lowering quality. If you need an exact file size as well as exact dimensions, set both and the tool will handle them together; see compress to a size.
A related setting, DPI, only matters for printing and does not change pixel dimensions; the guide to pixels, DPI and resolution explains the difference, and change DPI sets it directly. Your image is processed in your browser and never uploaded.