The safest starting point is the application itself: identify the document, the country, and whether the photo is being uploaded, printed or both.
The measurement first
Millimetres and inches describe physical output; pixels describe digital dimensions; DPI connects pixels to physical size during printing. If an authority already states the required pixel dimensions, use them directly. If you are building a print file from millimetres, the basic relationship is pixels = millimetres × DPI ÷ 25.4.
Where calculations stop being enough
A mathematically correct file can still fail because the face is the wrong size inside the frame, the background is unsuitable, the compression introduces visible artefacts, or the application expects a different file type. Finish every conversion with a visual and application-specific check.
When the rule is strict
Prefer a fresh, controlled capture over aggressive software repair. A clean original is easier to defend and easier to reuse for another legitimate application route.
Exam portals are moving targets
Exam and recruitment bodies can change their upload fields, file-size caps, and application instructions between cycles. That is why a responsible guide should explain the preparation method rather than hard-code one number forever. When you open the current notification or portal, copy the stated photo dimensions and file limits into your checklist, then use the image tool to meet them.
Keep the clean master portrait. It is common to need a second version later—for example, a different pixel size, a different crop, or a smaller file for another form.
Practical detail to carry forward
When you are done, open the final file once more from disk rather than from the editor. That confirms the exported file—not just the preview—contains the intended crop and dimensions.
Entrance Exam Photo Size in Pixels
Start with a clean source and use FastIDPhoto for the practical preparation steps, while the official authority remains the final acceptance decision.