Here is a very detailed cheat sheet to use when trying to make sure that your images are the correct size on several different social media sites – including Facebook, Twitter, Google Plus, Linked In, and Pinterest.
Have you ever uploaded a picture to one of these sites, only to find that the picture didn’t look right? This is probably because if your picture is not the correct size the site will attempt to make it fit within the dimensions that it requires. It might stretch the image and make it look distorted or really blurry if the original image was too small. On the other hand, if it’s too big then you might find that portions of the image have been cropped off in order to make it fit. Most of the sites will allow you to select the specific part of the image that you want to display, but you might still have to leave off certain sections of your image.
Alternatively, you could take a quick look at this cheat sheet and find the correct dimensions that each site requires for the image you are posting. Once you have the correct dimensions you can open the image in any image editing program (including Microsoft Paint) and re-size it to fit within those requirements.
The awesome people at LunaMetrics spent a lot of time researching and analyzing each of these sites to determine the optimal dimensions for your images.