You can get massively different results depending on how you have set it up -
is a good source of info and testing for VPN's as it takes consideration of the compression that takes place to data being sent/received via a device connected to a VPN.
This tests how much data can be downloaded at once, which is your MB/s, the other main factor is latency/ping (how long does it take your data to get from point a to point b).
Id recommend trying this even if you dont use a vpn -