As previous comments mentioned, Pagespeed Insight and Pingdom.
Also I would like to add https://gtmetrix.com/
In my opinion, those tools should give you an idea only and not be used as definite answers.
As there are various factors that affects the load speed for each user around the world. Like distance from origin server and users internet speed.
I would like to add, test different pages on your website not only homepage. In my case Homepage is pretty fast but when it comes to sub-pages the score/speed differs quite a bit.
note: with the tool i have mentioned, page load may differ from one test to another for unclear reasons.