Tumblr Dashboard Image Display Sizes (Updated March 20, 2016):
- Photo Post: 540 by 810 pixels for dashboard view. Use 1280 by 1920 pixels for high-res version (except for superwide panoramas).
- “Tall” Photo Post: Tumblr takes a 300-by-810-pixel version of your image then stretches it by 80% using HTML height and width attributes to make it 540 by 1458 pixels. Image quality may be diminished. Aim for uploading at least 710-by-1920-pixel images in case Tumblr switches to a better image size on the Dashboard. (It’s happened before.)
- Photoset: 540-pixel width for one image in a photoset row. 268-pixel width for two images in a photoset row. For three images in a photoset row, Tumblr displays 177 pixels on the left and right images and 178 pixels for the middle. Gutters are 4 pixels.
- Audio Post: 169 by 169 pixels for album art.
- Link Post: 540 pixels wide for the image grabbed by Tumblr from the web link (if available).
- Text Post: As of March 30, 2015, inline images can appear full-width (540 pixels wide). Any inline images that are 300 pixels wide or larger will display as full-width.
- Avatar: 64-by-64-pixel icon next to posts.