Before worrying about whether the child is sleeping enough or not, keep following things in mind:
For a newborn, baby sleeps 17 to 18 hours normally per day. For a one year old baby, it sleeps for 10 to 12 hours per day.
Like adults, children also have different variation in sleep patterns and hours. There is no fix chart for their sleep.
So if a child stays happy, eats well and stays active all during the day then whatever sleep the child takes is usually enough.