this post was submitted on 19 May 2025
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This beats the approximations used in ancient Sumer (3.1065) and China (3). Try contacting their respective records bodies.
Gotta say, using 3 just feels like giving up due to laziness, even in 1200BC.
Also it's interesting how the Chinese entries basically stop between 1400 and 1949, whereas European names are far more present during this era. Some Japanese ones, too. I wonder how comprehensive this page is.
Rounding pi to 3 is just the engineering way. It's close enough to get the job done and then I don't have to worry about decimal places. However, using pi=3 typically undershoots your calculations, so personally I like to use pi=4
I finally found you, an engineer actually using π=3 (or 4 as you say), and not just people making fun of it.
I am also an engineer, but I'm going to wager much more recently graduated (worked 3.5 years).
Who hurt you?
Like, I get it, in a world before calculators, but there's a button on the calculator, in your spreadsheet, in whatever program that approximates pi to many, many, many digits.
Putting in a design/safety margins into pi seems like a strange choice.
Sincerely, an engineer looking for answers on this π=3 meme.
Even if it's back of the napkin first past approximation. You have a phone calculator. Please use it for our collective peace haha
(All jibes in jest, I'm genuinely curious)
Only 7 years of engineering experience and pretty much every time I have used pi, I have rounded it to 3 or 4. Now, the thing is, I am an electrical engineer that works in industrial automation. I never use pi at all
Thanks for the response! Still, why would you do this, and not just use pi?
I'm not following what the purpose of rounding pi is
PI() is the function a spreadsheet, if that helps ;)
Please give me peace haha
An error margin of less than 5% (even better, biased in a known direction) is more than good enough for plenty of use cases.
An error margin of more than 25% on the other hand, is seldom acceptable.
Nah, it's fine. Trust me I use pi=4 in every calculation I do that uses pi and I haven't ever run into any issues at all
(I'm not that type of engineer, I never do anything with pi)
One is an error margin, the other a factor of safety!
It's called safety factor
Sometimes zero decimals is enough precision even in 2025…
…but also because of laziness…
AFAIK the Chinese knew that the value between that of the encompassing shape that meets the circle at tangeants to the inscribed shape whose edges meet the same equidistant points gives us the approximation of pi. So did archimedes, and maybe even the babylonians.
So while a triangle yields about 3 and satisfies the theorem, you could also theoretically draw a 96 gon and 192 gon like Liu Hui for an accuracy of 9x10^5.
Personally I just memorize 22/7 or use the Leibniz infinite series if I have to.
Doesn't have the famous
for some reason. Accurate to 14 decimal places I believe which is more accurate than what you need for 99.9% of its applications.
So to avoid memorizing a 15-digit number you'll memorize a 13-digit equation?
More like you memorize that to show off. There are tons of high schoolers that know pi to dozens of digits, it’s not really exciting. But most high schoolers fundamentally don’t understand logs.
It's been said that with 15 decimals, you can calculate the circumference on the observable universe with a precision of the width of an atom.
It's also been said that with Pi to just four decimal places you can accurately send a spaceship to one of our nearest neighbouring stars and arrive within one kilometre of your intended target.
In fairness, that was said by me, and I do tend to be full of shit.
Not quite, according to JPL https://www.jpl.nasa.gov/edu/news/how-many-decimals-of-pi-do-we-really-need/
15 decimal places, for Voyager 1 - We have a circle more than 94 billion miles (more than 150 billion kilometers) around, and our calculation of that distance would be off by no more than the width of your little finger.
This is an exaggeration.
The universe's radius is around 46.5 billion light years (around 4.4 * 10^26 meters), the error introduced of using 15 decimals of pi is around the order of 10^-16. Thus the error of calculating the circumference would be in the order of
What's it it's a big ass atom?
It's 39.
14 decimal places is more accuracy than you'd ever need.
Consider the size of what you're measuring.
I'm American so you're getting SAE units, deal with it.
If we have a radius of 1", the circumference of my object is 6.283185 or so inches around. Maybe it's 6.283186. the difference between those two numbers is one one hundred thousandths of an inch. About 25 nanometers. Half the size of the smallest bacterium we've ever discovered.
That is with 6 decimal places. With 8 you can measure a circumference with an accuracy to the single atom. Any smaller than that, and you start charging the result by measuring it at all.