Rough guess, about 15. We live on the outskirts of Reading and the 4+ mile journey to the centre takes about 30 mins. All depends on traffic and how busy the bus is.
and how often it stops On the outskirts of reading the bus probably stops quite a few times, whereas on the a4 it'd do the distance quicker as the stops are spread out
It all depends on traffic, how many stops etc.
It takes me 12-15 minutes to travel 1.5 miles on local bus.
Can you check a timetable...that might help by giving departure and arrival times.
10-15 minutes urban, 4-8 minutes rural. Rough estimate. But very difficult to predict not knowing the route etc.
The two most common journeys which I make vary considerably. The 5-mile (as the crow flies) journey takes 20-25 minutes on a good day (Hayling Island to Havant). The 3-mile (ditto) journey takes 35-40 minutes (Havant to Waterlooville).
I've just checked a timetable for a town route in Ipswich. A journey of 2.3 miles (which is not much different to the one you're asking about) takes 15 or 16 minutes, depending upon the exact route taken.
However a similar length journey on the route through our small town (using a straight country road with very few stops or other hold ups) takes only about 8 minutes.