Daniel Tammet, 25, took just over five hours to perform the feat, sitting in front of a blackboard once used by Albert Einstein before an audience at Oxford University’s Museum of the History of Science.
Pi is the ratio of the circumference of a circle to its diameter: 3.14159 continuing as an infinite series.
Mr Tammet, from Herne Bay, Kent, is recognised as one of a select band of so-called "savants" - people capable of extraordinary mental feats linked to medical conditions.
Unlike the central character in the film Rain Man, starring Dustin Hoffman as the autistic savant Raymond, Mr Tammet developed his extraordinary ability to "see" numbers after childhood epileptic seizures.
While he has outgrown his early disability, multilingual Mr Tammet remained able to perform unusual feats of memory and has founded a company teaching people skills for learning maths and languages.
On Sunday, he displayed his skills, reciting Pi to 22,514 decimal places, breaking the previous European record in a bid to raise money for the National Society of Epilepsy.
Yesterday, he said the task was similar to "running a marathon in your head". He joked: "I slept very, very well last night."
The physical constraints of performing the feat in front of witnesses far outweighed the difficulty of actually learning the number, he said. "It took me a few weeks to learn the number, and that was backwards as well as forwards; it wasn’t a problem for me at all. I would even go so far as to say it was actually rather easy.
"It was, as I had thought, a physical challenge for me just sitting there for such a long period of time under invigilation conditions and not fidgeting or getting so tired that I couldn’t go on. That is one of the parallels with something like running the London Marathon; towards the end it was getting very tiring."
David Josephs, of the National Society for Epilepsy, said: "This is a fantastic achievement. Daniel’s success gives out a very positive message about epilepsy - the condition need not affect someone’s ability to use their brain nor stop them aspiring to great achievement."