Medium range is 20 meters. It is about 2 "tiles" in NWN2, viewable from the toolset or if you guess in game. Interior tiles are slightly smaller, so it is about 2.1 tiles or so inside.
20 meters in feet is around 65 feet.
3.5E notes[]
Medium range in 3.5E is defined as:
Medium: The spell reaches as far as 100 feet + 10 feet per caster level.
Because of NWN(2)'s CRPG sizes, that is the area's buildings and distances are not to any real life scale, this doesn't fit, and would be unbalancing (the Long range in NWN2 actually is 131 feet, thus about the maximum medium range in D&D!). The maximum range at level 20 is still a good 300 feet! (around 3 times the distance viewable in NWN2).