Carrie UnderwoodCarrie Underwood doesn't have any children yet, but she's hoping to have a few eventually -- and the Oklahoma native says four is more than enough.

"Not that I have a husband to have one with yet, but someday I'd like a family," she tells Self magazine. "Not a big one, but not a small one either. Two kids is good, three is fine. Four? Somebody's getting something done, because we ain't having five!"

Carrie doesn't mention who the father of these future children might be, but she's been dating Ottawa Senator hockey player Mike Fisher for quite a while now. One thing's for sure, Carrie would be one hot mama -- especially since she takes such good care of herself. She actually gets her training -- for free -- from 'The Biggest Loser' celebrity trainer Jillian Michaels, but not because of her celebrity status. The 'Cowboy Casanova' singer, who's on just about every publication's most beautiful list these days, says, "I have Exercise TV on cable. Jillian Michaels' videos will kick your butt. She's my trainer, and she doesn't even know it!"

In addition to her workout routine, Carrie has lowered her sugar intake, including cutting out soda and just eating healthier.

Carrie will take her svelte and healthy body on the road, when her Play On tour kicks off March 11 in Reading, Pa. Tickets for all shows go on sale this Friday (Dec. 18).