How many hours a day should my baby be sleeping?

12-18 hours usually. Babies sleep almost 16-20 hours when first born, so in theory they could do nothing but eat and sleep and they'd be fine. As they get a little older, that can go down, but generally 12 to 16 hours is a normal level. The real question is, how are they when they are awake? If alert, happy, and energetic, then they are doing fine.
Depends on his age. Babies need less sleep as they age. The following is the average amount of sleep babies need at different ages; each individual baby is slightly different. Newborns: 16-18 hr/day (half during the day, half at night) 3 months: 15 hr/ day 9 months: 14 hr/day (but now it's 10 hr at night, 4 during the day) 2 years old: 13 hr/day (most at night with a 2 hour nap) 4 year old 11 hr (no nap).