| Format | Size in cm | Pixels at 300 PPI |
|---|---|---|
| A5 | 14.8 × 21 | 1748 × 2480 |
| A4 | 21 × 29.7 | 2480 × 3508 |
| A3 | 29.7 × 42 | 3508 × 4961 |
| A2 | 42 × 59.4 | 4961 × 7016 |
Image Resizer
Resizing changes the number of pixels in an image. Done properly, a photo keeps its proportions and stays clear wherever it is shown.
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See all toolsWhat resizing an image means
A digital image is a grid of pixels. A 4000×3000 photo is 4000 pixels wide and 3000 pixels high. When you resize, software calculates a new grid, smaller or larger than the original.
Reducing is usually safe, because surplus information is dropped. Enlarging is riskier: the software has to invent pixels that do not exist, and the image gradually softens.
How to keep the proportions
The ratio of width to height has to stay the same, or faces and logos look stretched. If the target format has a different ratio, crop the image instead of squeezing one axis.
- Start from the best original you have.
- Decide where the image will be used and what size is needed there.
- If the ratios differ, crop first.
- Reduce to the required size and save the result as a new file, so that you keep the original.
How many pixels print needs
In print, what matters is density: how many pixels fall on each inch of the finished piece. For documents and material seen up close, the usual value is 300 PPI. A large banner seen from several metres can work at a lower density, so the exact value depends on the material and the viewing distance.
Sizes for the web
On a website, an image should not be much larger than the space it fills. A 6000-pixel photo in an 800-pixel column only slows the page down. For high-density screens, it is sensible to prepare about twice the displayed size.
Frequently asked questions
Does resizing lose quality?
When reducing, detail shrinks with the size but the image stays clear. When enlarging past the original size, it softens, because the new pixels are calculated rather than recovered.
What is the difference between resizing and compressing?
Resizing changes the number of pixels. Compressing keeps the pixel dimensions but reduces the weight of the file.
Can a phone photo be printed as a poster?
Often yes, but it depends on the photo's resolution and the viewing distance. Compare its pixel size with what the format needs at a suitable density.
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