The working distance for wireless is usually specified in the product description (either on the packaging or in the manual). Problem is, claims for 1000 feet or 300 metres are based on clear line of sight which is not how we usually use these products in the home.
The actual reliable working distance for most wireless networking may be about 60 feet or through three walls.
My own wireless 802.11g system connects a computer at the front of the building to a router at the rear and down one floor. The distance could be around 25 feet (say 9 metres) plus 3 walls. It's not entirely reliable with occasional loss of connection for under a minute.
You may achieve better performance with 802.11n products.
You achieve worse if the building uses a lot of metal or has foil insulated drywall partitioning.