Are 4 vials of Sculptra on each hip a good estimate for me to round out my hip dips? (photos)

If you need more than four vials, you will automatically figure that out with the end result. No one has a crystal ball though. There is also a risk of overcorrection. You may want to consider minimal/gentle liposuction of the outer thighs so they don’t stick out beyond the dip. That said, your physique looks good enough as it is already. Sometimes the enemy of good is better. Why take the risk of ruining the physique you already have? Spend that money on books for school, a nice sushi dinner, a down payment for your future home, or helping those less fortunate.

Sculptra unlike other fillers increases volume as it induces collagen production. So the solution itself is not the one that produces the added volume. The process relies on the body's natural collagen production. It induces the body to produce collagen. The chances of it looking natural are very high because of this too. And so, because of this, we will never promise or guarantee that a certain number of syringes/vials will be sufficient to reach your goals. This will depend on your individual response to treatment. You may start with 10-12, and then decide whether you want more or not.

Thanks for your question.  Sculptra to the buttock region can be an option in patients that don't have a great deal of fat for fat transfer and that looks like you.  As mentioned on this thread no one has a crystal ball about how much will be necessary but in my practice I have seen best results with the range you reference.  Best wishes.