Exam PhotoThe rule in one line
Pixels = centimetres ÷ 2.54 × dots per inch. There are 2.54 centimetres in an inch, and "dots per inch" says how many pixels sit along each inch when the picture is printed.
Ready answers
| Paper size | At 100 dpi | At 200 dpi | At 300 dpi |
|---|---|---|---|
| 3.5 cm × 4.5 cm (passport photo) | 138 × 177 | 276 × 354 | 413 × 531 |
| 6 cm × 2 cm (SSC signature) | 236 × 79 | 472 × 157 | 709 × 236 |
| 3.5 cm × 1.5 cm (CTET signature) | 138 × 59 | 276 × 118 | 413 × 177 |
| 3 cm × 3 cm (thumb impression) | 118 × 118 | 236 × 236 | 354 × 354 |
| 10 cm × 5 cm (declaration) | 394 × 197 | 787 × 394 | 1181 × 591 |
Which dpi should I choose?
If the notice names one, use that. IBPS and SBI, for example, name 200 dpi and also give the pixels (240 × 240 for a 3 cm thumb impression), so there is nothing to work out.
If the notice gives only centimetres, any dpi gives the right shape. A higher dpi means more pixels and a sharper picture, but also a bigger file. For small KB limits such as 10 to 20 KB, 200 dpi is a sensible middle. What matters to the form is the shape, the file size and that the picture is clear.
Why a form may reject a "correct" size
A picture can be the right number of centimetres on paper and still fail, because the form checks the file: its type (JPG), its weight in KB and sometimes its pixels. Resize the file, not the printout. The resize tool does all three checks for you.