Back in the day, the bodybuilder's diet (for growth) was the infamous 40/40/20. That is, 40% of calories from Protein, 40% of calories from Carbs, and 20% of calories from Fat. If we look at the rule of thumb: 1.5g per lb (weight), we can work backwards.
Let's say my weight is 210 pounds:
Knowing that 1 gm of protein is 4 kcals
Calculate Daily Total kcals:
(Protein represents 40% of our diet)
Since carbs are the same percentage and same kcal per gram (energy) as protein, it's easy to calculate them.
(total kcals - (Protein + Carbs)) = Fat
Which leaves us with 315 grams of protein, 315 grams of carbs, 70 grams of fat per day.
With all of that said... 3150 appears to be a high number to me. Am I missing something?