What ceiling height does a golf simulator need?

About 2.7m internally at an absolute minimum, and 3m if you want to swing without thinking about it. Taller golfers need more. Because internal height is whatever is left after the floor and roof build up, it has to be designed in from the start rather than discovered on site. A 6m x 5m footprint is a comfortable starting point for a simulator with room to stand back and watch.