How much time is the shuttle run from BWI airport to BWI Amtrak station?

Although the Google info provided in @PeterM's answer is mostly correct, I've ridden that shuttle multiple times in both directions, between BWI Airport and BWI train station, and the only "multiple" stops are the couple of stops it makes at the airport terminal itself. Once it leaves the terminal, it goes directly to the train station (or leaving the train station, it goes directly to the airport). Though be watchful of the stops at the airport side, as not all of them are open all of the time. Although the information says they run every 10 minutes, that can fluctuate due to road traffic, passenger loading, etc. They can sometimes bunch up, where a couple busses come in short order, then there's a 15+ minute wait for the next one.

Just make sure to look for the proper bus, as there are several independent bus routes at BWI airport, one for the train station, one for the car rental facility, one for long term parking, and there could be another as well that I'm not remembering.