sparty sezz:
Ok, I just don't see 4/3 NM-B at Home Depot or Lowes. And yes I
already knew I needed 4 lines, 2 hots, 1 neutral, 1 ground.

Try a real electrical supply...I would be suprised if they even have 6/3 (at
least my locals). It was spendy but worth it for my situation.

From my reading, you don't want more than a 2% drop in Voltage, so as
long as it is under 100 feet you are ok.

Sounds right for the drop recommendation but I haven't run your numbers...

When you say 100A are you saying that is your main breaker panel that
you are running this from, or that is the size of the breaker you
added to your main breaker panel, to run to your new one?

I added a 100A breaker in my main panel to supply my 100A sub-panel.
--
Later,
D-Rog