I have been wondering how to do this for a while and accidentally discovered it while perusing this heroku page. ab is the ApacheBench marking tool, it lets you set how many requests (for better averaging) and how many concurrent requests (for load testing) to send to your website. ab id installed by default on most unix/linux/mac os x.

50 requests 2 at atime

$ ab -c 2 -n 50 http://amaras-tech.co.uk/

Outputs:

This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking amaras-tech.co.uk (be patient).....done


Server Software:        nginx
Server Hostname:        amaras-tech.co.uk
Server Port:            80

Document Path:          /
Document Length:        0 bytes

Concurrency Level:      2
Time taken for tests:   9.951 seconds
Complete requests:      50
Failed requests:        0
Write errors:           0
Non-2xx responses:      50
Total transferred:      11400 bytes
HTML transferred:       0 bytes
Requests per second:    5.02 [#/sec] (mean)
Time per request:       398.030 [ms] (mean)
Time per request:       199.015 [ms] (mean, across all concurrent requests)
Transfer rate:          1.12 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      146  162  16.7    158     214
Processing:   149  229 198.3    159    1113
Waiting:      148  228 198.2    159    1112
Total:        298  392 198.0    328    1262

Percentage of the requests served within a certain time (ms)
  50%    328
  66%    343
  75%    351
  80%    360
  90%    612
  95%    961
  98%   1262
  99%   1262
 100%   1262 (longest request)