My husband and I are trying to put together a 100 or 125 amp breaker box on a pole to establish utilities to our home. We already have some 4 gauge copper wiring and we're not sure if this will support the amperage. Is there some kind of table or guide? The other thing is that the electric company must OK it. Will it?

I think #4 copper should be fine for 100amp not sure for anything larger until you get to 200amp which at least here in sc #2 copper is required. Here you also need a #6 copper for ground for 200amp service I think #8 should be okay for grounding 100amps. Most importantly check with your local building codes usaully permits are required for doing this type of work. This is from my best memory based on where I live . Wherever you are may have different requirements that I am unaware of. Im sure TK will be on later and he will no doubt have the answers if I have missed anything.

AC is correct. For residential 100 amp feeder, #4 copper is allowed.

The utility should be fine with it. Best to check with them before getting in too deep, as they may have other requirements.