This question is hard to answer because it depends, first, on the amount or size of bones. On top of this, the density of a person's bones varies with gender, age, diet, history and activities. Men have denser bone then women, on average. Bones become more dense as cartilage becomes woven bone and then laminar bone. Then bone becomes less dense as people get older and absorb/store less calcium and use more reserves.
The average adult skeleton weighs 30-40% of the total mass of the person, but this is only a rough estimate assuming a normal BMI. so if a persons weight is ~ 150lbs, their bones weigh ~50lbs
An adult's skeleton is made up of around 30%-40% of their total body weight, and half of this weight is made up of water. Basically, at birth a newborn baby is made up of over 300 bones, while on average an adult has a total of 206 bones. Find out more details here http://en.wikipedia.org/wiki/Human_skeleton.