Wirless AP effective range

Check the vendor specification and divide it by two, then you might get a somewhat fair distance at clear line of sight and average weather.

The other issue is the type of material that the signal is trying to through.  Brick walls, metal walls and doors, safety glass windows, and concrete are the worst and will significantly degrade your signal.  If you have those types of materials, you can subtract from the estimates given above.

In open space the usable distance could be significantly further than inside a house, for example.  We need to know what the gain of the antenna is for a start but you didn't tell us which external antennas you have.