Printing pretty filesizes in a Drupal theme

drupal-theme-filesizes.php

/*
 * Takes a filesize integer and returns a decently formatted string
 * This function needs to go into template.php, don't forget to change the theme name below
 * Call it like this:
 * - print mytheme_format_filesize($node->field_downloads[0]['filesize']
 */
function mytheme_format_filesize($filesize) {
	
	if ($filesize < 1024) {
		return $filesize . ' bytes';
	} 
	elseif ($filesize < 1048576) {
		return round($filesize / 1024) . ' kB';
	}
	else { 
		return round($filesize / 1048576) . ' MB';
	}
	
}