Gravatars are Globally Recognized Avatars. By default, WordPress uses gravatar to display user’s avatars based on their email. The default size for WordPress’s avatars is 48px which is pretty small. A lot of sites these days are using much larger avatars, a trend that I really like.
I’m using Genesis Framework and below code snippet works perfectly for me to change Default Avatar Size. Just put below code to your Child Theme’s functions.php file.
// Modify Default Gravatar Size
add_filter( 'genesis_author_box_gravatar_size', 'crunchify_author_box_gravatar_size' );
function crunchify_author_box_gravatar_size( $size ) {
return 90;
}
Another must read:
For other WordPress Framework or Other default theme’s i.e. Magazine Premium, TwentyThirteen, TwentyTwelve, etc. You may want to take a look at get_avatar function (most probably in your theme’s functions.php file).
Ref: http://codex.wordpress.org/Function_Reference/get_avatar