Every TikTok image size
TikTok needs only two image sizes: the small square of your profile picture and the full vertical frame used by photo posts and video covers.
Video cover / photo post
1080 × 1920 px, 9:16 Full screen. The app draws buttons on the right and the caption at the bottom.
Profile picture
200 × 200 px, 1:1 Shown as a circle.
Photos for TikTok photo posts
A photo post fills the screen like a video. A 3:4 phone photo loses a band on each side to become 9:16; a landscape photo loses far more. Shoot vertically when you know a photo is for TikTok.
The app places its buttons along the right edge and the caption across the bottom. Keep faces and text away from those areas so they are not covered.
Only the first line or two of the caption show over the photo, so put the point of the post there.
Covers that make your profile readable
A cover is what people see on your profile before they tap. A consistent style (the same font, the same place for the title) turns a grid of random frames into something a visitor can scan.
Make the cover at 1080 × 1920 here, keep the title in the middle so the grid crop does not cut it, and choose it as the cover when you post.