Centimetres to pixels, at the DPI your form expects.
Exam notices describe some images in centimetres (a 3.5 × 4.5 cm photo, a 6 × 2 cm signature box) and check others in pixels. The two only meet through DPI, the number of pixels printed per inch. Pick a size and a DPI below to get the pixels, or go the other way. The third panel reads the DPI stored inside a JPG or PNG and, for a JPG, saves a copy with the DPI you choose.
Size to pixels
Passport size. 413 × 531 px at 300 DPI, or 276 × 354 px at the 200 DPI many bank notices ask you to scan at. The bank portals themselves check 200 × 230 px, so use that when your notice gives pixels.
Pixels to size
The pixel count is the same at every DPI. Change the DPI and only the printed size moves: 200 px is 2.54 cm wide at 200 DPI and 1.69 cm at 300 DPI.
Check or change the DPI of a photo
Reads the DPI stored in a JPG (JFIF and EXIF headers) or PNG. For a JPG you can then save a copy with a new DPI number. Only the header changes; the pixels and the picture stay exactly as they were.
The formula
One inch is exactly 2.54 cm, or 25.4 mm. So pixels = centimetres ÷ 2.54 × DPI, rounded to a whole pixel. A 3.5 cm width at 300 DPI is 3.5 ÷ 2.54 × 300 = 413.4, which becomes 413 px. Going back, centimetres = pixels ÷ DPI × 2.54, so a 200 px wide photo prints 5.08 cm wide at 100 DPI and 2.54 cm at 200 DPI.
Exam sizes worked out
| Box | 200 DPI | 300 DPI | What the portal checks |
|---|---|---|---|
| Photo 3.5 × 4.5 cm | 276 × 354 | 413 × 531 | 200 × 230 px on the bank portals; check your own notice |
| Signature 6 × 2 cm | 472 × 157 | 709 × 236 | File size and fill, no pixel count |
| Thumb 3 × 3 cm | 236 × 236 | 354 × 354 | 240 × 240 px (IBPS and SBI notices) |
| Declaration 10 × 5 cm | 787 × 394 | 1181 × 591 | 800 × 400 px (IBPS and SBI notices) |
Notices round. IBPS and SBI call a 240 × 240 px thumb impression "3 cm × 3 cm" at 200 DPI, though the exact figure is 3.05 cm. When a notice gives both, the pixels are what the upload page measures.
What DPI changes, and what it does not
A JPG stores its DPI as a small number in the file header, in the JFIF block, the EXIF block, or both. Setting it to 200 or 300 does not add detail, does not resize the photo, and does not change how it looks on a screen. The file size stays the same, or grows by 18 bytes if the file had no JFIF header to hold the number. What it changes is the printed size: a 240 px wide image prints 3.05 cm wide at 200 DPI and 8.47 cm wide at 72 DPI.
Most exam portals ignore the number. They check the pixel size and the KB range, so a photo at the wrong pixel size fails with any DPI. The exceptions worth knowing are the IBPS and SBI thumb impression and handwritten declaration, where the notice states 200 DPI. The IBPS notice reads: Dimensions: 240 x 240 pixels in 200 DPI (Preferred for required quality) i.e. 3 cm * 3 cm (Width * Height). File Size: 20 KB - 50 KB.
(CRP PO/MT-XVI detailed notification (30.06.2026), Annexure III, Guidelines for Scanning and Upload of Documents (PDF page 40)). The thumb impression and handwritten declaration tools already write 200 DPI into their output.
If you need a different pixel size, change the pixels with the photo resizer and then set the DPI here. Doing it the other way round loses the DPI, because resizing makes a new file.
Reading the DPI of a photo
- Camera photos usually carry an EXIF resolution of 72 DPI. Windows Explorer and Photoshop read EXIF first, so when a file has both blocks the reader shows the EXIF figure and the changer updates both.
- JPGs saved by a web browser, and by many apps, store a JFIF header with no unit. That means no DPI at all, and Windows fills in 96. The reader says so rather than inventing a number.
- PNG files keep their resolution in a pHYs chunk, in pixels per metre. The reader converts it to DPI. The changer handles JPG only, since exam portals ask for JPG.
Common sizes
One-click presets for the sizes exam forms ask for most.
Frequently asked questions
- How many pixels is 3.5 × 4.5 cm?
- At 300 DPI it is 413 × 531 pixels. At 200 DPI it is 276 × 354 pixels. The formula is pixels = centimetres ÷ 2.54 × DPI, rounded to a whole pixel.
- Does changing the DPI make my photo sharper or bigger?
- No. DPI is one number in the file header that tells a printer how many pixels to fit in an inch. Changing it here leaves every pixel as it was, so the photo looks the same on screen and the file size moves by at most 18 bytes. To make a photo bigger or smaller you have to change its pixel size, which the photo resizer does.
- Do exam portals check DPI?
- Almost all of them check only the pixel size and the file size in KB. IBPS and SBI do state 200 DPI for the thumb impression and the handwritten declaration, so setting 200 DPI on those files matches the notice. A photo with the wrong pixel size will still be rejected whatever DPI it carries.
- Why does my JPG show 96 DPI on Windows?
- Files saved by browsers and many phone apps store no DPI, only an aspect ratio. Windows shows 96 DPI for those files. The reader on this page tells you whether a DPI is really stored and whether it sits in the JFIF header, the EXIF block, or both.
- Why does the notice say 240 × 240 px for a 3 × 3 cm thumb when the maths gives 236?
- 3 cm at 200 DPI is 236.2 pixels. IBPS and SBI rounded the box up to 240 × 240 px and still call it 3 × 3 cm. The portal checks the pixels, so upload 240 × 240. The same happens with the declaration: 10 × 5 cm at 200 DPI is 787 × 394 px, and the notices ask for 800 × 400.
- Is my photo uploaded when I check or change its DPI?
- No. The file is read and rewritten in your browser. Nothing is sent to a server.