The number of digits of pi Emma Haruka Iwao calculated in 2019 was itself pi: exactly 31,415,926,535,897 — π times 10 trillion.

On Pi Day 2019, Google's Emma Haruka Iwao computed π to 31,415,926,535,897 decimal digits — a figure that is itself π times 10 trillion.

When Emma Haruka Iwao finished her calculation on March 14, 2019 — Pi Day, naturally — the number of digits she had computed was itself a version of pi. She had pushed Archimedes' constant to 31,415,926,535,897 decimal places. Line those digits up next to the constant they describe and you see the joke the universe seems to have set up: 31,415,926,535,897 is π multiplied by 10 trillion. The length of the answer echoed the answer.

Iwao, then a developer advocate at Google Cloud, laid out the whole run in a company blog post titled "Pi in the sky: Calculating a record-breaking 31.4 trillion digits of Archimedes' constant on Google Cloud." It was no stunt done on a laptop. The figure — "31.4 trillion decimal places—31,415,926,535,897 to be exact, or π × 10^13," as the post put it — earned a Guinness World Record for the most accurate value of pi, a title NPR and The Washington Post both reported at the time.

How do you compute 31 trillion digits of pi?

You do not do it by hand, and you do not do it with a single machine. Iwao ran the calculation on Google Compute Engine, renting a cluster of virtual machines in the cloud rather than building a dedicated supercomputer. The software was y-cruncher, a program written by Alexander J. Yee specifically for computing mathematical constants to absurd precision. It is the tool behind most modern pi records.

The scale is the hard part. A single trillion digits already overflows any ordinary amount of memory, so the computation has to shuttle intermediate results across many terabytes of storage. Iwao's run used 25 virtual machines working for roughly 121 days straight, churning through about 170 terabytes of data — comparable, as she noted, to the entire printed collection of the Library of Congress. Any hardware failure or network hiccup during those four months risked corrupting the whole thing, which is why cloud infrastructure, with its redundancy and ability to restart from checkpoints, made the attempt practical in a way earlier record-setters' hand-built rigs did not.

How do we know the number is right?

Here the "verified" part earns its keep. A record like this is not simply announced — it is checked by recomputing the final digits using an independent mathematical formula, a standard verification step that y-cruncher performs. If two different methods agree on the last stretch of digits, the odds that the whole result is wrong become vanishingly small. Guinness World Records accepted the computation on that basis.

Iwao's achievement also beat a specific predecessor. Her blog framed the prior record as roughly 22.4 trillion digits, but the precise figure deserves precision in an article about precision: Peter Trueb set the earlier mark in 2016 at 22,459,157,718,361 digits, a number The Verge's Jon Porter cited correctly in his coverage. Iwao added nearly nine trillion digits on top of that.

There is a tidy symbolism to a woman computing pi to pi-times-ten-trillion places on Pi Day. Iwao has said she'd been fascinated by pi since childhood, and the record was both a genuine mathematical result and a demonstration of what commodity cloud computing could do — anyone, in principle, could rent the same machines.

What stays open is the obvious question: why bother? The digits of pi have no practical use past the first few dozen; NASA navigates spacecraft with about fifteen. The honest answer is that these runs are stress tests for hardware and algorithms, benchmarks that expose subtle bugs long calculations would hide. And the record never holds. Since 2019 the mark has fallen again, more than once, each new number longer and stranger than the last — pi, true to form, refusing to end.