it depends on your maintenance, what your goals are, and how much fat you are willing to gain. It is alot to be answered without a lot of info on you. If you don't need much to grow, than 4000 may make you fat, but their are people out thier that need up to 5000 to grow. If you normally eat 3000 calories a day, i would probably start upping it by 500 like fantom said. But remember the more muscle you put on, that 3500 will likely become your new maintenance, and you will need to up it again if you plan on getting bigger. The more muscle you hold, the higher your maintenance calorie intake should be.