On 14 March at 1.59pm GMT, Professor Marcus du Sautoy will host Pi Day Live, a free interactive online event that is open to all. Pi Day Live welcomes as many people as possible to work together to calculate pi using techniques from the pre-computer age. We want to discover if we can collectively calculate pi to one, two, three or more, decimal places using tools no more sophisticated than marbles, sticks and string. Anyone can take part, via our online lecture theatre or by watching online on the ‘big screen’.  All you need is a computer that can run YouTube to be able to get involved.