PHP BCrypt rounds -- aproximate calculation time
CPU: Intel(R) Xeon(R) CPU  E5620  @ 2.40GHz

Cost 4           Time 0.00152s		<1 sec
Cost 5           Time 0.00283s		<1 sec
Cost 6           Time 0.00549s		<1 sec
Cost 7           Time 0.01068s		<1 sec
Cost 8           Time 0.02113s		<1 sec
Cost 9           Time 0.04198s		<1 sec
Cost 10          Time 0.08359s		<1 sec
Cost 11          Time 0.16706s		<1 sec
Cost 12          Time 0.33389s		<1 sec
Cost 13          Time 0.69307s		<1 sec
Cost 14          Time 1.4942s		1 sec
Cost 15          Time 2.59085s		2 sec
Cost 16          Time 5.17141s		5 sec
Cost 17          Time 11.01445s		11 sec
Cost 18          Time 21.36687s		21 sec
Cost 19          Time 42.72507s		42 sec
Cost 20          Time 85.22791s		01:25 min
Cost 21          Time 168.58197s	02:48 min
Cost 22          Time 339.44701s	05:39 min
Cost 23          Time 676.54287s	11:16 min
Cost 24          Time 1353.63319s	22:33 min
Cost 25          Time 2706.78602s	45:06 min
Cost 26          Time 5436.3684s	01:30:36 h
Cost 27          Time 10972.12116s	03:02:52 h
Cost 28          Time 21868.52597s	06:04:28 h
Cost 29          Time 43960.10345s	12:12:40 h
Cost 30          Time 88339.33714s	24:32:19 h
Cost 31          Time 176139.059s	48:55:39 h


#!/usr/bin/env php
<?php
        $found = 31;
        for ($cost=4; $cost<=31; $cost++) { // 4..31 is the valid range of PHP Bcrypt
                $x = time();
                $start = microtime(true);
                password_hash("TEST", PASSWORD_BCRYPT, array("cost" => $cost));
                $time_elapsed_secs = microtime(true) - $start;
                echo "Cost $cost => Time ".round($time_elapsed_secs,5)."s\n";
        }
?>