if you havent deleted the history then wehn you make an object (if you done have interactive creation on) everythings is set to a scale of 1x1x1 or the size of 1cm x 1cm x 1cm (depending on your preferences) so back to the point a circle at a scale of 1 should fit a sphere of 1, (I think LOL!) Not got maya open at the emo to check.