Webpagetest is one of the most popular and free tools for measuring webpage performance. 

Webpagetest enables you to run web performance tests on your site from a number of different locations across the world in a number of different browsers.

Wevpagetest gives you values for following parameters of your webpage

• Load Time – Time requires to load the page
• First Byte Time – Time when your request started to execute
• Page Size – Total Size for your Web page
• Requests – Number of Requests your Webpage made.