New Google+ Plus Header Image Size
The new header that Google has come out with in March, 2013 has these dimensions…
- 1060 pixel width
- 600 pixel hieght
So the head is 1060×600 pixels in size.
The profile picture appears as a circle and hovers over the image at 145 pixels from the bottom of the image on the left so account for that space being blocked.
For a complete list of sizes for social media banners, check out this page.