You can use online tools such as GTMetrix and Pingdom to check your WordPress website speed. We recommend you use Pingdom which gives quite good results. Make sure you choose a server close to the place where your site is hosted. Clearly, if your site is hosted in London, and you select a test server in the United States, the result will not be representative of the site’s true loading time.
Tools such as Google PageSpeed does not actually measure the speed of your website but gives performance scores/ratings which are just an indicators of good practices. Good scores/ratings do not guarantee a fast site and vice versa.