Quick answer
Pixels measure an image on screen; cm, mm and inches measure it on paper. DPI (dots per inch) links them: pixels = inches × DPI. A 3.5 × 4.5 cm photo at 300 DPI is 413 × 531 pixels. Use Resize image to set the exact size in any unit.
How do pixels and cm relate?
Pixels = inches × DPI, and 1 inch = 2.54 cm. So at 300 DPI, 1 cm ≈ 118 pixels.
| Size | 200 DPI | 300 DPI |
|---|---|---|
| 3.5 × 4.5 cm | 276 × 354 px | 413 × 531 px |
| 2 × 2 inch | 400 × 400 px | 600 × 600 px |
| 4 × 2 cm | 315 × 157 px | 472 × 236 px |
Which DPI should I use?
- 300 DPI for printing photos.
- 200 DPI when a form says so (PAN does, for example).
- For online-only forms, the pixel size and KB matter more than DPI.
How do I resize to an exact size?
- Open Resize image.
- Enter width and height and choose the unit: px, cm, mm or inch.
- Choose the DPI.
- Choose what happens if the shape differs: Crop, Fit or Stretch.
- Click Resize and download as JPG or PNG.
Leave height empty to keep the original shape.
Then fit the KB limit
If the form also has a KB limit, finish with Resize image to KB.
Frequently asked questions
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