Lab puppy growth

Question
How much should my lab pup weigh if he is seven months old?

Answer
Nobody can answer that without seeing the dog.  I am not sure my 8 month old Holly weighs 40 pounds yet.  Other healthy Labs might weigh twice that.  There is an easy way for you to learn to asses his weight, see
http://www.puppychow.com/products/popup_body_condition.aspx  Adjust what you are feeding as needed to reach his ideal body condition.  

Switch to an adult chow if not already.  It slows growth giving more time to develop sturdy joints.  Make the switch over about a week to avoid digestive distress.