unwrapping:

Tumblr Dashboard Image Sizes (Updated March 30, 2015):

• Photo post: 540 by 810 pixels for dashboard view. Use 1280 by 1920 pixels for high-res version (except for superwide panoramas).
• Photoset: 540-pixel width for one image in a photoset row. 268-pixel width for two images in a photoset row. 177-pixel width for three images in a photoset row. Gutters are 4 pixels.
• Audio Post: 169 by 169 pixels for album art.
• Link Post: 130 by 130 pixels for the thumbnail image grabbed by Tumblr from 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.