Smarty Modifier filesize

create a file in the plugin directory called: modifier.filesize.php

then add this code:

<?php
/**
 * Smarty plugin
 * @package Smarty
 * @subpackage PluginsModifier
*/

/**
 * Smarty replace modifier plugin
 * 
 * Type:     modifier<br>
 * Name:     filesize<br>
 * Purpose:  show the filesize of a file in kb, mb, gb etc...
 * 
 * @param string $ 
 * @return string 
*/
function smarty_modifier_filesize($size)
{
  $size = max(0, (int)$size);
  $units = array( 'b', 'Kb', 'Mb', 'Gb', 'Tb', 'Pb', 'Eb', 'Zb', 'Yb');
  $power = $size > 0 ? floor(log($size, 1024)) : 0;
  return number_format($size / pow(1024, $power), 2, '.', ',') . $units[$power];
} 
?>

then you can use: {$filename.size|filesize}

assuming the size you are giving is originally in bytes,

try this:

{if $size lt 1024}
  {$size} bytes
{elseif $size lt 1048576}
  {$size / 1024}Kb
{else}
...
{/if}