Adding new image size in wordpress

Define the new image size in your functions.php
add_image_size( ‘cat-thumb’, 98, 113,true );

Now we have defined a new image size with size 98X113 and name ‘cat_thumb’.
Third parameter shows, if we need hard crop the image with the defined size. Otherwise we can omit the third parameter.

Call the image size using: the_post_thumbnail(‘cat-thumb’);