The first calculation of pi was made by Archimedes of Syracuse (287–212 BC), one of the greatest mathematicians of the ancient world. Archimedes approximated the area of a circle by using the Pythagorean Theorem to find the areas of two regular polygons: the polygon inscribed within the circle and the polygon within which the circle was circumscribed.
Since the actual area of the circle lies between the areas of the inscribed and circumscribed polygons, the areas of the polygons gave upper and lower bounds for the area of the circle.
Archimedes knew that he had not found the value of pi, but only an approximation within those limits. In this way, Archimedes showed that pi is between 3 1/7 and 3 10/71.
Pi has been known for almost 4000 years—but even if we calculated the number of seconds in those 4000 years and calculated pi to that number of places, we would still only be approximating its actual value. Check out this brief history of finding pi: from Exploratorium.edu.
Mathematics is a field that many people shy away from, but there are some who had a passion for numbers and making discoveries regarding equations, measurements, and other numerical solutions in history.
Here's a list of names and accomplishments of the greatest mathematicians of all time shared by Famous-mathematicians.org.