How many hours is enough for our sleeping?

In the present era human being is getting very busy day by day and every person from a little child to the the young men to the old people everybody is busy in their daily routine and we are forgetting about our health problems and our rest time because we need to make progress in this world and want to earn more and more money and we are sacrificing rest and enjoyment for this purpose and also we are ignoring our sleep hours. According to the doctors 8 hours of sleep is needed by the body.