The sleep of toddlers departs from the sporadic, disruptive sleep of infants and begins to transition to the sleep patterns of younger children. This can be a confusing time, so let's go over what's normal and what's not.
First, let's keep in mind that toddlers are defined as kids who are just beginning to walk (or "toddle") and typically are 1 to 3 years old. Most children in this group will sleep less as they get older and the need for daytime naps will decrease.
A child who is 12 months old will sleep on average eight hours per night. These one-year-olds may take short naps that last 1 to 2 hours and occur a few times per day.
By the time your child is 18 months old, they may sleep 8 to 10 hours at night and take just one daytime nap lasting 1 to 2 hours.
Most 2-year-olds will continue to sleep 8 to 10 hours at night and take one nap per day that lasts 1 to 2 hours. In total, these children may even sleep as long as 12 to 14 hours per day on average, most of which occurs during the nighttime.
By the time you are ready to start your child in preschool, by the age of 3 or 4, the amount of sleep needed may decrease to 11 to 12 hours total. Naps may still occur, but by the time your child is ready to start kindergarten many children no longer require daytime naps.
Durmer, JS et al. "Pediatric Sleep Medicine". Continuum. Neurol 2007; 13(3):153-200.