This is the commonly used size: we found no requirement published by the institution. Confirm it before your application.
Tips to get it right the first time
Limits change between cycles: check the photo section of the current UPSC notice before uploading.
Use the same recent photo you will carry to the exam; it is matched against your face at the venue.
The signature is a separate JPG: sign in black ink on white paper, as the notice describes.
How to do it with Requisito Listo
Open the «UPSC application photo» template in the app.
Take the photo with the on-screen guide (or pick one from your gallery).
The app centers your face, makes the background white and gets the exact size and file weight.
Check the checklist, then upload or save it.
At the end you'll see a checklist: size, file weight, background and format. If something doesn't comply, it tells you what to fix before the portal rejects it.