I am a big fan of using Safari's built in Web Inspector for this sort of task.
Open Safari preferences, go to Advanced and tick the check to show the Develop menu in the menu bar.
Now you can refresh a page and see detailed information on the Timelines section to graph page load times, delays and whatever sequence of steps was needed to render the current page.
You can also use command line tools like
curl in conjunction with the
time command or using curl's internal timing options
curl --trace-time to pick apart some of the files or scripts if you want to get a statistical level of repeatability as opposed to a broad overview of an entire page load.