The Telegram Profile Picture size (512×512px)
Telegram displays profile pictures as circles, so a square 512x512 source is the safe choice: the app crops your square to a circle, clipping the corners, so anything important needs to sit within the central circular area. At 512x512 the avatar has plenty of resolution to look crisp everywhere Telegram shows it, from the tiny circle in a chat list to the larger view when someone opens your profile.
This size is the same square Telegram uses for its own image assets, and it downscales cleanly to the small avatars in group chats and channels. Uploading at 512 gives the app good pixels to shrink from, avoiding the softness you get when a too-small image is stretched to the profile view. Telegram also lets you set a profile video, but for a still image, a well-sized 512x512 photo is the reliable baseline.
For a face or logo, keep the subject centered so the circular crop frames it neatly, and give a little breathing room so the top of a head or the edge of a mark is not clipped by the circle. High contrast helps the avatar stand out in both Telegram's light and dark themes, which many users switch between. Everything here resizes 100% in your browser with no upload and for free, so your photo stays private on your device. Telegram occasionally updates avatar handling, so verify the current recommendation if you want a pixel-perfect result.