If you don't want to rely on the internet speed checkers built into search engines, then another option is to download an app. My app of choice, which is available for a wide range of platforms, is Ookla SpeedTest. I find this service offers a fast, reliable, and accurate test.
I use these tests regularly, both when out and about and when at home or the office. It offers a bit of an internet health check and lets me keep an eye out for possible problems with my network and internet connection.