Royston is the third-largest of the four towns in North Hertfordshire when measured by population. The relative isolation of the town means that it plays an important service role for many of the surrounding villages in both Hertfordshire and Cambridgeshire. At the time of the 2011 census the town had a population of 15,781 and there were 6,800 dwellings in the town. Development of the town has tended to be informed by the busy roads running through and around the town and the Cambridge-to-London railway line that bisects the town.
The town grew up around the crossroads of the ancient Icknield Way and Ermine Street, although the market place is not at the crossroads itself but to the south-east. One theory as to why the market is not at the crossroads is that Ermine Street originally approached the town from the south-east along Grange Bottom, avoiding the steepest parts of the hill to the south, and that the present line of High Street / London Road is a result of medieval realignments. The town centre is covered by a conservation area.