This pi calculator can calculate a rough estimate of pi it uses the Leibniz Formula This is a simple but slow-converging series: "π/4 = 1 - 1/3 + 1/5 - 1/7 + ..." That's why its not way accurate as I can't do 10000000000000 calculations of "1 - 1/3 + 1/5 - 1/7..." Or else it would take days to calculate.
This took awhile to get working plz like and fav :)