<?php
    // get the start time as UNIX timestamp (in millis, as float)
    $tstart = microtime(TRUE);
 
    // start outout buffering
    ob_start();
 
    // display your page
    include 'some-page.php';
 
    // get the number of bytes in buffer
    $bytesWritten = ob_get_length();
 
    // flush the buffer
    ob_end_flush();
 
    // how long did the output take?
    $time = microtime(TRUE) - $tstart;
 
    // convert to bytes per second
    $bytesPerSecond = $bytesWritten / $time;
 
    // print the download speed
    printf('<br/>You\'ve downloaded %s in %s seconds',
        humanReadable($bytesWritten), $time);
    printf('
 
 
 
<br />Your download speed was: %s/s',
        humanReadable($bytesPerSecond));
 
    /**
     * This function is from stackoverflow. I just changed the name
     *
     * http://stackoverflow.com/questions/2510434/php-format-bytes-to-kilobytes-megabytes-gigabytes
     */
    function humanReadable($bytes, $precision = 2) { 
        $units = array('B', 'KB', 'MB', 'GB', 'TB'); 
 
        $bytes = max($bytes, 0); 
        $pow = floor(($bytes ? log($bytes) : 0) / log(1024)); 
        $pow = min($pow, count($units) - 1); 
 
        // Uncomment one of the following alternatives
        //$bytes /= pow(1024, $pow);
        $bytes /= (1 &lt;&lt; (10 * $pow)); 
 
        return round($bytes, $precision) . ' ' . $units[$pow]; 
    }