How many amps does 4 use wire carry?

What is 4 use wire? You mean 4 conductor? In any case, it depends on the wire gage and whether it is stranded or solid conductor. Look on the side of the wire. There will likely be something printed or empossed on the insulation like the following: 4-18 which would mean 4 conductor, 18 gage wire. Single conductor wires will have the AWG directly on them such as: 12AWG or 10AWG as used in homes. Find out the gage and reply. Then I can tell you the amperage limit for the wire.

Out of curiOSity, .... why do you want to know? Are you adding more load to the wire? If so, you should also consider the fuse that protects the wiring. It's rating will be lower than that of the wire so it fails first.