As you know, Google+ is Google’s social network. Founded in 2011, it already has more than 300 million active monthly users. This is the appearance that a profile on the site has:

Google Plus Cover Photo Size

– The maximum cover image size can be up to 2120 x 1192 px
– The minimum cover image size can’t be less than 480 x 270 px
– The recommended cover image size is 1080 x 608 px.

Google Plus Profile Photo Size

– Profile image size is 250 x 250 px

Google Plus Image Size

– The size of images shared in the newsfeed is 497 x 373 px.
– The size of the images for links shared in the newsfeed is 150 x 150 px.

Appearance on devices:

Although G+ uses a responsive design, so images automatically adapt to different devices, to ensure the max quality of appearance on screens, tablets and smartphones, they suggest uploading images whose size is no less than 502 x 250 pix, nor greater than 1080 x 608 pix, otherwise some information will be lost.

Credit: https://postcron.com/en/blog/social-media-image-dimensions-sizes/