What are common social media image sizes?

You can find common social media dimensions here (measured in pixels). Updated 16 June 2015.

Facebook 
Facebook cover: 851 x 315
Facebook profile: 180 x 180 (displays 160 x 160, thumbnail at 32 x 32)
Timeline image: 1200 x 630 (max feed display 470, max page display 504, 1:1 ratio)
Shared link: 1200 x 627
App image: 111 x 74

Twitter 
Twitter header: 1500 x 500
Twitter profile: 400 x 400 (displays 200 x 200)
Shared image: 440 x 220 (2:1 scale, 1024 x 512 max)
5 MB maximum file (or 3 MB for gifs)

Google+ 
Google+ cover: 2120 x 1192
Google+ profile: 250 x 250
Shared image: 497 x 373 (can be uploaded and viewed up to 2048 x 2048)

LinkedIn
LinkedIn cover: 1400 x 425
LinkedIn profile: 500 x 500

Pinterest 
Pinterest profile: 165 x 165
Pinterest board, large thumbnail: 222 x 150
Pinterest board, small thumbnail: 55 x 55
Pins on main page: 236 x Scaled height (expanded at 600 min)

YouTube 
YouTube cover: 2560 x 1440 
YouTube cover safe area: 1546 x 423