Here is a quick list of the image dimensions for some of the most popular social media networks around. Let us know if you see a change out in the wild.
Last updated 11/1/17
Facebook
Cover Photo
828 x 315 pixels
Profile Photo
Larger than 180 x 180 pixels
Displays as 160 x 160 pixels
Shared Image
1200 x 900 pixels
PShared Image (Preview)
Displayed at 1200 x 628 pixels
Twitter
Header Photo
1500 x 500 pixels
Profile Photo
Upload 400 x 400 pixels (recommended)
Displays as 200 x 200 pixels
Timeline Images
506 x 253 pixels
Instagram
Profile Picture
110 x 110 pixels
Displays as 200 x 200 pixels
Shared Images
All images are square.
1080 x 1080 pixels
Shared Video
1080 pixels wide
Google+
Profile Picture
250 x 250 pixels (recommended)
Displays as a circle 125 x 125 pixels
Cover Photo
1080 x 608 pixels
Shared Images
Less or equal to 506 x 284 pixels wide
Shared Video
506 pixels wide
LinkedIn
Personal Profile Picture
Ideal upload between 200 x 200 and 500 x 500 pixels, no dimension over 4000 pixels