Code to Add Additional Image Sizes in WordPress

Default WordPress automatically creates several image sizes when you upload an image. You can also create additional image sizes to use in your theme. Add this code your theme’s functions file.

add_image_size( 'sidebar-thumb', 120, 120, true ); // Hard Crop Mode
add_image_size( 'homepage-thumb', 220, 180 ); // Soft Crop Mode
add_image_size( 'singlepost-thumb', 590, 9999 ); // Unlimited Height Mode

This code creates three new image sizes with different sizes. Feel free to tweak the code to meet your own requirements.You can display an image size in anywhere in your theme using this code.

<?php the_post_thumbnail( 'homepage-thumb' ); ?>