After three months, infants can often sleep for about 8 hours at a time, with most of that sleep at night. Starting after about 3 months of age, infants begin to be able to put themselves to sleep. At this age, babies usually sleep about 10.5 hours at night. For naps, they usually sleep for a total of about 3.75 hours.
Adapted from Jellinek, M. (2000). Bright Futures in Practice, Mental Health