Sleep—we all need it and it accounts for a third of our entire lives. But how much sleep is ideal, and how, with work, kids, and everything else going on in our lives, can we reach the goal? The short answer is that there is no magic number of hours of sleep that is optimal for everyone. Most studies say that between eight and nine hours of sleep is considered the optimal amount for us to wake up feeling completely restored and rejuvenated, but many people can function on three to five hours, and some people need at least 10.