It depends on what kind of wire/cable you are using. If you use NM-B or UF-B you need to use the 60° column. If you are running individual wires in conduit, then you can use the 75° column.

There are a lot of rules with a hot tub that need to be followed carefully, if you're not a 110% certain of what you are doing, hire a licensed electrician.

Here is a link that might be useful: Wire Ampacity Chart

I assume that was 230VAC not 203 (which would be a rather uncommon residential voltage). The spa does indeed draw 40A continuous with all the pumps and heaters that are allowed to run together running, but the surge of the motor start or whatever mandates 50A. You must follow this recommendation..

Contrary to what Mike is implying, most NM and UF are NOT LEGAL for this purpose. The outside parts of the wiring must have a insulated ground and the sheath of the cable does NOT qualify.

The #8 is correct for the THWN (75°) or (THHN or THWN-2) (90°) you are likely to be legally using for this purpose.

Forgot about the insulated ground, my mistake. Just out of curiosity, why does the ground need to be insulated.

Also I'm curious if could one run NM to the disconnect (say it was mounted on the side of the house) and then individual wires (including the insulated ground) in conduit to the spa? Or does it need to be an insulated ground all the way back to the panel?

If you're on the 2008 or later code, they have clarified it that you can run a sheathed cable as long as the ground is in the sheath on the inside part of the run.

Before 2008 it was ambiguous so you were kind of at the whim of your local jurisdiction.

The insulated ground is required by code and that's all I care about. Personally I don't dwell on why in this case.

For a single family dwelling you CAN run NM cable, or any other NEC Chapter 3 wiring method, inside the structure. Once you leave the structure you must follow Art.680 wiring methods and rules.

Ron, I never read that as ambiguous. I was always under the impression that NM was OK for the inside part for spas and pools.

I am not home so I can't look up the actual wording of previous editions right now.

Thanks for all the info provided.
One (hopefully final) question... Most of the 50amp wiring from the main panel will run through the basement of the house, but then it needs to go outside to the GFCI panel. Does some different wire need to be used for the inside and the outside parts?

My other thought was to put in a 100amp outdoor panel, fed from the main 200amp panel of the house (this would give me some additional capabilities for lights etc later on). The GFCI could then connect to this 100amp sub-panel (it would only be about 15' to the GFCI.

Petey...the insulated ground on the inside portion of wiring for outside spas/pools was ambiguous and there was lots of arguing about it on the forums. The NEC added text to the 2008 code that made the use of NM explicitly OK in the 2008 code.

Hmmm, I never experienced that. No prob.