How many computer chargers can I put on 1 electrical outlet?
36 laptops,
or
144 tablets,
or
18 laptops and 72 tablets,
or
Any combination of laptop and tablet that is less than or equal to 1440 watts.

Since a 15 ampere 120 volt circuit can supply a maximum of 1800 watts, but a circuit should only be loaded at 80%.  

15 amperes * 120 volts = 1800 watts

1800 watts * 0.80 = 1440 watts

This example assumes that this is a dedicated circuit, with no other loads on the circuit.