I know how to set the size of a post thumbnail image using the WP Admin Media Settings or using this function:

set_post_thumbnail_size( 150, 150 )

But how would one get the image width and height that have been set for an image thumbnail size?

I'd like to be able to do something like this:

get_post_thumbnail_size(); // return array(150, 150)

How would this be done? Is it by using get_option(), and would the options keys be for thumbnail width and height?

7 Answers 7


When an image size is added either by WordPress(add_image_size), or by a plugin or your own custom code it gets added into the $_wp_additional_image_sizes global, i can't find a similar function for pulling data from that global, but you could certainly just look inside the global to determine what width and height a registered image size has.


global $_wp_additional_image_sizes;
// Output width
echo $_wp_additional_image_sizes['post_thumbnail']['width'];
// Output height
echo $_wp_additional_image_sizes['post_thumbnail']['height'];

Of course just be sure to reference those values at a point after you've set the size. So if for example you're setting the thumbnail size during init, you'll need to make sure to do whatever you need to after that point(else you'll get back the sizes as they were prior to setting them).

Hope that helps.

  • It appears to be post-thumbnail rather than post_thubmnail (WP3.6) Commented Sep 23, 2013 at 9:38

There is however another way:

get_option( 'thumbnail_size_w' );
get_option( 'thumbnail_size_h' );

Note: thumbnail is one of the sizes set inside $_wp_additional_image_sizes. So the call to get_option() will work for every other image size too.

  • 4
    This is actually the best option because plugin can run their hooks on it.
    – fuxia
    Commented Feb 10, 2012 at 13:55
  • 1
    That's why I am surprised it hasn't been mentioned yet.
    – Mark
    Commented Feb 10, 2012 at 14:00
  • This doesn't seem to work for custom image sizes?
    – Loosie94
    Commented Mar 16, 2022 at 14:46

The only thing still missing is the thumbnail's ID:

$post_thumbnail_id = get_post_thumbnail_id( $post_id );
$attachment = wp_get_attachment_image_src( $post_thumbnail_id );
  • Actually this is the only really useful answer for all possible cases, especially when not in post's context.
    – Picard
    Commented Oct 30, 2021 at 11:02

As an addition to why it's such a pain to retrieve these numbers, a core enchancement that contains a finished patch. Sadly it's still not in core.

Just follow the progress of this ticket: Wordpress Trac: Enchance get_intermediate_image_sizes() to contain not only the names, but the sizes too.


Keep in mind that this global $_wp_additional_image_sizes; might not work as expected. For example when using is in plugin it will not return the additional sizes that a Themes have registered.

  • It will if you make the call later enough in the action sequence, ie. if the theme registers the sizes on the init action, your call must be made after that action has occured.
    – t31os
    Commented Apr 11, 2013 at 19:08

What you need is this function: wp_get_attachment_image_src

Codex: http://codex.wordpress.org/Function_Reference/wp_get_attachment_image_src

It will return an array containing attachment's url, width and height.

  • 1
    Yes but it expects an ID for a given image, the user doesn't have an ID to pass, he wants to find out the registered size by name, eg. thumbnail(post_thumbnail).
    – t31os
    Commented Dec 19, 2011 at 13:12

In addition to the post above:

$attachment = wp_get_attachment_image_src( $attachment_id ); // where $attachment_id is the ID of the attachment you want to get the thumbnail from

Then simply use the next code to display the url, width and height:

echo $attachment[0]; // url
echo $attachment[1]; // width
echo $attachment[2]; // height

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