According to the National Kitchen & Bath Association planning guidelines, the recommended minimum size for knee space at a counter is 17" deep. In our house we have only 13" of overhang and it works well for us because we have small backless stools which are only 14 x 14". We also have an adequate pathway behind the stools for traffic.

If you keep your counter height stools small, they will fit better into a smaller space and they will look better. I'm not fond of big barstools that swivel and have backs and arms.

Be sure to talk to your cabinet person and granite fabricator about the overhang because usually any overhang more than about 12" needs support under it as granite is actually a somewhat fragile material that can break if not supported sufficiently from below.

Our overhang is 12, and is more than adequate.

Carolyn is right - the granite needs to be supported. About every 30", there should be some kind of bracket, whether it's wood to match the cabinetry, or a metal L-bracket, which isn't seen.

12" should be fine.

I am planning on 12" minimum and 15" as comfortable

thank you all helpfull comments