What size in pixels is 3.5 × 4.5 cm?
A size in cm becomes pixels only once you choose a DPI (dots per inch). The same 3.5 × 4.5 cm photo has a different pixel size at each DPI:
| DPI | 3.5 × 4.5 cm photo | 2 × 2 inch photo | 6 × 2 cm signature |
|---|---|---|---|
| 96 | 132 × 170 px | 192 × 192 px | 227 × 76 px |
| 150 | 207 × 266 px | 300 × 300 px | 354 × 118 px |
| 200 | 276 × 354 px | 400 × 400 px | 472 × 157 px |
| 300 | 413 × 531 px | 600 × 600 px | 709 × 236 px |
The formula is pixels = cm ÷ 2.54 × DPI, rounded to the nearest pixel. If your form gives the size in pixels, choose pixels instead and type them in; the DPI then does not change the size.
DPI, cm and KB: how they fit together
A form usually sets three things, and this tool keeps all three:
- Size in cm or mm and a DPI fix the exact pixel width and height. The tool always gives you exactly that, cropped or fitted, never stretched.
- The DPI is also written inside the JPG file, so a portal that reads it sees the value you chose.
- The KB limit is reached by changing only the JPG quality, because the pixel size is fixed. 1 KB counts as 1,000 bytes for the largest size, so the file passes whether the portal counts in 1,000 or 1,024.
If the tool says the size does not fit your KB limit, the pixel size is too big for that many KB. Lower the DPI, or check that the size and limit you typed match the form.
Crop to fill or fit inside
Crop to fill (the default) fills the whole size with your picture and cuts off what does not fit. Drag the box, or use the arrow keys, to choose which part to keep. Fit inside keeps the whole picture and adds white bars where the shapes differ, which suits a signature or a document you must not cut.