Will I be able to dunk when i grow up I am 5 ft 1 at age 11 and can touch 8 ft?

There is no way to know at this point. There are many factors that are unknown. How tall you will be. How much exercise you will get(how strong you will be). How large your feet will be (Yes, this helps).

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Height has little to do with one's ability to dunk a basketball. Look at Tyrone Curtis "Muggsy" Bogues, who retired from the NBA as a player in 2001. At 5' 3", little Mugsy, one of the best ball handlers in NBA history, was able to dunk pretty much on demand.

The key is to develop the ability regardless of perceived limitations.