How does Google Analytics calculate Avg Page Load Time?

Question

How does Google Analytics calculate the Avg Page Load Time and what is taken into consideration while calculating Avg Page Load Time?

Let's assume I have an HTML file that refers to a few CSS files, JS files and images and this HTML makes a few AJAX calls, inside the jQuery document.ready() event.

Is Page Load Time the sum of the download times of the items below or does it exclude any of them?:

1. Download time of HTML file
2. Download time of all CSS files
3. Download time of all JS files
4. Download time of all images
5. AJAX calls response time

Answer 1

pnuts' comment above is accurate. I wanted to also offer some suggestions on tools to help optimize site/page performance.

Google Chrome, Firefox, Internet Explorer, and Edge have development tools to mimic load times over different network speeds.

Two common sites used to rate a page on a website's performance are:

GT Metrix:  https://gtmetrix.com/

Pingdom Tools:  https://tools.pingdom.com/

Both GTmetrix & Pingdom Tools provide guidance/information as to what steps to take to address each warning/flag in the performance report in their web interface. GTmetrix's results can be downloaded in the form of a PDF to share with others.

In addition to the above, Google offers PageSpeed Insights: developers.google.com/speed/pagespeed/insights