What size wire and conduit is needed for a 125 amp, 120/240 volt, 4 wire , sub panel?

I'd use no less then #6, Don't forget your copper ground from main panel to new sub panel:::::

I just wired up one that way, but I am feeding it from only a 60 amp breaker. I think the full 125 amps needs something heavier.

Min size is #2 copper,or #1/0 aluminum for residential feeder.

Should not guess at wire sizes.

As I said, I thought you needed heavier wire. tkrussell knows you do. He knows the conduit size too, but may have let the #6 wire answer distract him from saying so.

Hey tkrussell:::- I hit the wrong key , I' just learning on the type writer keys . In fact I' m still doing what my son said, 9hunt sand peck. but I'mtrying.After I get done I look over whaty I just done and try yo correct my mistakes. I'm not going to redo thisd one F.B.E.

You Can Also Consult Your Nec For Your Wire Ampacities And Sizes Of Your Conduit...