Babylonians simply made a big circle, and then measured the circumference and diameter with a piece of rope. The Babylonians used this method to find that pi was slightly greater than 3, and came up with the value 3 1/8 or 3.125. Estimating 4 accurate digits of pi

Gave pi the the value of 3.14166, correct of 4 digits, which he obtained from Archimedes polygonal algorithms.

Created a polygon-based algorithm and used this theorem to calculate a 3,072-sided polygon to figure out the value of pi.

Later invented a faster way of calculating pi and the rounded value of 3.14 by using a 96-sided polygon. Knowing that the differences in area of the two polygons, he figured out the polygons made a geometric factor with the number 4. Liu Hai calculated pi to 5 digits - 3.1415

Calculated pi equaled around 355/133 by using Hui's algorithm, applying it to a 12,288 sided polygon. With a correct assumption of the first 7 digits of pi in the form of "3.141592920" remained the most accurate approximation of pi for the next 800 plus/minus years to come.

Islamic mathematician produced 14 digits of pi using a polygon with 3×2 (to the 28th power) sides.

Indian mathematician discovered the ' Madhavan - Leibniz Series ' a infinite series that calculated pi to 11 decimal places - 3.1415926535

German mathematician who is famed for his calculation of π to 35 places. In Germany π used to be called the Ludolphine number.

Austrian astronomer Christoph Grienberger arrived at 38 digits, which is the most accurate approximation manually achieved using polygonal algorithms

English mathematician and physicist Isaac Newton used infinite series to compute pi to 15 digits using calculus

English mathematician who worked with Flamsteed. He calculated π to 72 places.