The average newborn sleeps about 16 hours a day, but some need much less sleep and some much more.
Also, it’s not uncommon for a newborn’s sleep pattern to change from day to day; he may sleep substantially less than usual one day and then “catch up” by sleeping more the following day. Let your newborn sleep as much as he likes as long as he wakes up to feed, and is eating adequately and wetting at least eight diapers a day. And let him sleep as little as he wants as long as he is not becoming overtired. But you’ll probably find that he sleeps for a large part of the day, waking primarily to feed and then falling back to sleep soon after. This pattern will change over his first few months as he gradually spends more time awake and alert.