As per comment from Ron Trunk i'll post this answer:
Depending on what kind of access point and the underlying network design/topology a rule of thumb is 15-25 but if its just web and email traffic you can have more. Just remember that you should have a gigabit port on the AP.
Also wireless is half duplex when you are calculating per device throughput. If you also enable 802.11n/ac that can cause your gigabit port on the AP to be your bottleneck. So you also have to take into account how many APs will connect to a switch and how the connection is from that switch back to your core.
Now for 50 some users/devices, I would, as written by Ron Trunk have at least 2-3 APs in that area and design that area for high density.