Average male guinea pig weight?

I just recorded my male guinea pig's weight and it looked like he was around 2.5-3 pounds. He eats well (like a pig) and he drinks normally. He gets treats about twice a day which include Kale (weekly),carrots,romaine lettuce,cucumber and occasional fruits. I'm not sure of his exact age but his fur was changing color about a month ago,starting right after I got him but it stopped now. I am guessing he is about a year old,or pretty close to it. I was wondering,is that normal weight for him?