How Do Google Measure Page Speed as a Ranking Signal?

When asked on Twitter about how Google actually go about measuring page speeds, Gary Illyes replied that the search provider currently ranks a site using a combination of PageSpeed Insights coupled with the actual page response times.

What Are The Differences Between The Two?
PageSpeed insights is a valuable online tool that will provide a detailed breakdown of on the time it takes the various parts of a webpage to load and you can try it out by visiting the following URL:

By entering the address of a given web page, Google will provide you with a detailed analysis that will offer advice on what to fix and how.

For example, the tool will report things like whether or not your images could be optimized (further), how to prioritize visible content and whether your CSS needs to be minimized in order to deliver a boost in performance.  This list is by no means complete, but it serves as a quick insight into the type of changes a webmaster should make to improve user experience across various devices.

In addition to PageSpeed Insights for Desktop users, there is also a User Experience test for those seeking to create Mobile Friendly Pages which load up quickly which can be used by visiting the following URL:

Page Response Time
The response time of a page is simply the actual length of time it takes the server to send all of the required resources to display a complete page to a visitor’s browser.  As you can probably see for yourself, PageSpeed Insights and Page Response Time are both related anyway so it is hardly surprising to hear Gary confirm that Google uses a combination of the two as an effective ranking signal.

By making use of the suggestions and fixes offered by Google, you should notice a decent performance increase across both metrics.