Find a schedule for the bus route you intend to use. These are often available at bus stops, from the bus service and online.
Locate your beginning stop on the route. This is often expressed as a corner or nearby landmark. Note the arrival time of the bus.
Locate your getting off point on the route. Note the arrival time.
Subtract your beginning time from your arrival time to figure out the run time. Remember that when working with time, there are 60 minutes in an hour (not 100, as in most other subtraction problems).
If you have a specific starting time in mind, use that time. If you want general information, select different starting times throughout the day to get an average run time.