The value of pi was likely first approximated by the ancient Babylonians. One Babylonian tablet estimated to be from around 1680 BC, provided a value for pi of 3.125. The Egyptians, a few year later, also calculated pi to a value of 3.1605. But, the actual first calculation of pi is believed to be done by Archimedes of Syracuse (287-212 BC).

Archimedes used the Pythagorean Theorem to first find the areas of two polygons –one which was drawn inside the circle and one which was drawn outside the circle. Archimedes knew the true value of pi was within the upper and lower bounds of his calculations.