Hi -- What is the proper conduit size for installing 4/0-4/0-4/0-2/0 Mobile Home Feeder cable? The meter box is on a pole about 25 feet from the house. The cable is rated for direct burial, but I think I should run the whole way in conduit because of the rocky soil.

I would use 3 inch Sch40 PVC conduit.

3" would allow an easier pull, but 2-1/2" would work fine as well.
Also, 3" will be harder to terminate in panels and enclosures. Most 200A equipment only has up to 2-1/2" factory knockouts.

Leadisheavy, You could always screen the rocks out of the soil for the bottom 6 inches!

Thanks for the info. I figured bigger would be better; I'll have to check on the knockout holes.

I figured bigger would be better; That is almost always a flawed philosophy.