As Google is placing increased emphasis and higher ranking to sites that load fast across multiple platform devices, here are 2 tools to help you evaluate the page speed of your site. Be forewarned, some of this feedback is pretty technical and you'll have to dig a little deeper, preferably with the help of your web developer.
• Test a sampling of the site's pages (Home, Product, Gallery, etc) with Google's Page Speed Insights. Record Mobile and Desktop Ratings.
• At the minimum your site should be faster than your competition's site, ideally your site should score in the above 80/100 range for both desktop and mobile tests if possible.
• Note that Google Page Speed Tests are to show you what improvements your page and site need, it's not an actual speed measurement.
• If the site is using Google Analytics, review the Behavior > Site Speed reports. The Page Timings section can be sorted by Avg. Page Load Time showing you the slowest pages on the site. Additionally you can show in the 2nd column the page Bounce Rate. Specifically make note of slow pages with high bounce rate for improvement.
• Next in the Google Analytics Site Speed section, the Speed Suggestions report will display pages that are ranked by Pageviews. Make note of pages with low scores and High Avg. Page Load Time for improvements.
An additional resource to test with is siteloadtest.com, this test is similar to Google Page Speed Insights, but also makes some additional recommendations you may find useful.
Credits: Search Engine News newsletter August 2014