my lab

Question
how much should a 18 month choc lab weigh

Answer
Nobody can give you a specific figure.  You need to feed it the right amount to keep it lean and let the weight be what it is.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them. Each dog is different. Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx