what distance is one square on a 1:50,000 OS map ?thanks?

Answer 1

One kilometre. If you measure the squares they're 2cm, multiply this by 50,000 to give you the distance. The squares on most large scale maps are 1 km, the 1:25,000 maps have larger squares. All OS maps in the Explorer, Landranger and Pathfinder series have 1km squares on them.