Coming up with the figure used about 170TB of data and took 121 days to complete.
Today is 14 March, also known as Pi Day (due to being written as 3/14 in the United States).
Iwao said she had help with the final calculation from Alexander Yee, who invented a program called "y-cruncher" for computing pi and other constants.
Iwao, who is based in Seattle, USA, achieved the feat by using Google's cloud computing service. "There is no end with pi, I would love to try with more digits", she said.
Iwao's calculation brings pi to 31,415,926,535,897 digits.
Iwao did her number crunching primarily from Google's office in Osaka, Japan, where she works at as a developer and advocate for Google Cloud.
The contstant is used in engineering, physics, supercomputing and space exploration - because its value can be used in calculations for waves and circles. It's almost nine trillion digits more than the previous world record set by Peter Trueb in November 2016.
Google announced her achievement Thursday - but Iwao has been striving toward this moment since she was 12 years old. A Yahoo engineer used the company's cloud tech in 2010 to calculate the 2 quadrillionth digit of pi, but did not calculate all the numbers in between. Saying the value of an irrational and transcendental number is quite a popular thing to do on Pi Day. Pi Day 2019: Know All About the Day As Math Jokes and Funny Memes Flood Internet.
"I liked computers when I was a kid", she tells NPR's Here & Now. "I was very fortunate that there were Japanese world record holders that I could relate to", Iwao said in the blog post.