Avebury is 29 miles from Salisbury station, about 50 minutes by shuttle. It sits on the A4361, west of Marlborough: 6 miles according to the National Trust, 7 according to English Heritage.
Your shuttle is a licensed private hire car run by Premier Taxis Salisbury.
By each way of travelling
On the bus, the second bus is the short part: Stagecoach’s timetable shows the 49 taking about 27 minutes from Devizes Market Place to Avebury Red Lion. There’s no direct bus, and on a Sunday neither bus route runs all the way.
Shuttle
About 50 minutes, with no changes.
Bus
Two buses with a change at Devizes or Marlborough; check the timetables for how long.
Bike
About 38 miles, about 4 hours of riding on National Cycle Route 45, by an OpenStreetMap route planner.
Avebury is in north Wiltshire, on the A4361 west of Marlborough. The National Trust gives it as 6 miles from Marlborough and English Heritage as 7. The nearest stations are Swindon, 12 miles away, and Pewsey, 11 miles away with no bus to Avebury, says English Heritage. From Salisbury the shuttle is the way with no changes.
How long to spend there
The bank and ditch around the henge are almost a mile round, says the National Trust, and its guided tours of the stone circle last about an hour. Allow time for the Manor, the museum and the café as well.
Avebury and Stonehenge
English Heritage says Stonehenge is within a 45 minute drive of Avebury.