Question concerning the use of 1” or 1 ¼” EMT. I’ve referenced the NEC tables for conduit fill, but I’m concerned about the ease of the wire pull, and the amp/derating factor, which I am not that familiar with, or if it even applies. Local code requires conduit. This is the set up:
1. Apprx. 11 foot run between service disconnect and panelboard.
2. Two 90 degree bends
3. 100 amp service
4. Feeders #4 copper labeled THHN
5. Bonding #8 insulated labeled THHN

So, for the above application- 1” or 1 ¼” emt? Thanks.

I would go with 1¼". 1" is legal but pushing it with two 90's.
You'll likely be able to pull it in by yourself with 1¼". With 1" you'll definitely need help.

If that conduit is outside which I assume it is make sure the wire is THWN. Many times the wire is dual marked THHN/THWN.

I like things easy so the 1 1/4" it is. Yes, the wire is dual marked THWN-2 or THHN

Why are you using #4 cable? If you selected this cable size because of T 310.15 in the NEC you need to be aware that this is for service entrance only.

If you are using this amperage to feed a sub-panel then you select the required cables size based on T 310.16.

Don, many areas still allow the use of 310.15(B)(6) for feeders as well as service entrance, and rightfully so IMO.