How To Test The Speed Of Your Website

To test the speed of your site, use the free tool from Pingdom. It's great, it gives you a break down of what's slowing your site(s) down. And it compares the speed of your site with others its tested in the past. Pingdom gives your site(s) a grade score, and shows you what you should do to improve its speed. I've used several tools on the internet to test site speeds, and Pingdom is by far the easiest to use, gives the best readouts, and offers the easiest to understand advice for correcting any issues your site may have.
Source: https://www.pingdom.com/
Source: https://www.pingdom.com/

GTMetrix is also a nice site to test the speed of your website. Where GTMetrix differs from Pingdom is GTMetrix actually allows you to compare the speed of your site with another site side-by-side. It also gives a grade for performance using metrics from YSlow as well. GTMetrix also offers a plugin for WordPress users.
Source: http://gtmetrix.com/
WP Plugin: http://wordpress.org/extend/plugins/gtmetrix-for-wordpress/
Source: http://gtmetrix.com/
WP Plugin: http://wordpress.org/extend/plugins/gtmetrix-for-wordpress/

Another cool website seed tester is WhichLoadsFaster. The only drawback to this site is it gets its data from another site, GTMetrix, which I'd use over WhichLoadsFaster anyway. But don't get me wrong, WhichLoadsFaster is great for a quick speed dual between two sites who's load times you were always curious about. Their results literally get displayed side-by-side by placing screenshots of their Home Pages next to each other. Cool. But as mentioned before, when you do a little further to get more in-depth information as to why one site performs better over the other site, WhichLoadsFaster connects you to GTMetrix for the bottom line data readout.
Source: http://whichloadsfaster.com/
Source: http://whichloadsfaster.com/