Pi has been approximated for about 3,600 years. Archimedes bounded it with polygons around 250 BC, Aryabhata gave 3.1416 in 499, and Madhava found infinite ser…
An Egyptian circle-area rule works out to pi of about 3.1605. Babylonian tablets imply 3.125. Practical rules, not yet a constant.
With 96-sided polygons inside and outside a circle he proved pi lies between 223/71 and 22/7: 3.1408 to 3.1429.
Zu Chongzhi showed pi is between 3.1415926 and 3.1415927. Nobody beat his bounds for about 900 years.
62,832 for a circle of diameter 20,000: 3.1416. He called it approximate.
Madhava found pi/4 = 1 - 1/3 + 1/5 - ..., added corrections and reached 11 decimals, 250 years before Leibniz.
Ludolph van Ceulen spent his life on polygons with up to 2^62 sides and reached 35 digits. They were carved on his grave.
His series for 1/pi add about 8 correct digits per term. Decades later they became the key to record computing.
Over a September weekend, ENIAC computed 2,037 decimal places using Machin's 1706 formula.
The Chudnovsky brothers' 1988 series adds about 14 digits per term. They passed 1 billion digits in 1989.
Fabrice Bellard computed 2.7 trillion digits on one desktop PC, and Alexander Yee released y-cruncher.
Emma Haruka Iwao of Google: 31.4 trillion on Pi Day 2019, then 100 trillion in 2022.
StorageReview: 2 AMD EPYC 9965 CPUs, 1.5 TB RAM, 40 SSDs, 110 days with no restart. Finished 19 November 2025.
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