τ Tau vs Pi

[KaladinsSenseOfHumourSpren He/Him]

I realised that there was no thread dedicated to this, so I decided to make one! Tau Day is coming up, after all.

For those of you who don't know, Tau is equal to 2π, and is an alternative circle constant. τ is good because if you use π, a full circle is 2π radians, but with τ, it's just one τ radians, which makes trig waaaaay easier.

So yes, I believe τ is objectively better than π, but I am also too used to π to swap now  

And also most calculators lack tau, and there's no song to help me memorise it, so...

Anyways, what do y'all think of tau?

Edited June 14 by KaladinsSenseOfHumourSpren
SPaG

[Through the Living Hopper He/Him]

At this point, π has used enough that it's probably going to stay what we keep using. Plus e^(πi) + 1 = 0.

Edited June 14 by Through the Living Hopper

[KaladinsSenseOfHumourSpren He/Him]

3 minutes ago, Through the Living Hopper said:

At this point, π has used enough that it's probably going to stay what we keep using.

Probably, but there's still a chance

3 minutes ago, Through the Living Hopper said:

Plus e^(πi) + 1 = 0.

Oh yes, something I forgot to mention...

With π, Euler's Identity is kind of clunky because you need the +1 to make it a zero

But with tau...

e^(τi) = 1

So yeah, another reason tau is better

[Through the Living Hopper He/Him]

1 minute ago, KaladinsSenseOfHumourSpren said:

With π, Euler's Identity is kind of clunky because you need the +1 to make it a zero

But with tau...

e^(τi) = 1

So yeah, another reason tau is better

Except, 1 and 0 are two identities. 1 is the multiplicative, and 0 is the additive. Having only one of those two doesn't fully let us appreciate the beauty of the formula.

[KaladinsSenseOfHumourSpren He/Him]

2 minutes ago, Through the Living Hopper said:

Except, 1 and 0 are two identities. 1 is the multiplicative, and 0 is the additive. Having only one of those two doesn't fully let us appreciate the beauty of the formula.

Yes, but e to the pi i doesn't equal 1, it equals negative one

The one is just there to make it a nicer number

[Through the Living Hopper He/Him]

Just now, KaladinsSenseOfHumourSpren said:

Yes, but e to the pi i doesn't equal 1, it equals negative one

The one is just there to make it a nicer number

Also to add another identity.

And that's a common way those formulas are written (to equal 0).

[KaladinsSenseOfHumourSpren He/Him]

2 minutes ago, Through the Living Hopper said:

3 minutes ago, KaladinsSenseOfHumourSpren said:

 

Also to add another identity.

 

Why are you adding the multiplicative identity ?

2 minutes ago, Through the Living Hopper said:

 

And that's a common way those formulas are written (to equal 0).

One works just as well

The extra +1 makes it not as good for π's

[Usseewa ✾ She♡They ✾]

the symbol for tau looks like half a pi (the right part of pi), so it's funny  that's it's 2pi..

[Chaos he/him]

Tau is so much better. It'd make learning the unit circle far easier. Half the circle would be tau/2. Way better!

In basically every physics formula, it's always 2pi. That really should indicate that 2pi is the correct one. I mean, when the hell do we even is C = pi * d? Use the radius! The radius is the important one. You might say, "But Eric what about A = pi*r^2?" To which I'd say, A = 1/2 tau*r^2 is very symmetric with the kinetic energy formula. That 1/2 should be there anyway, due to integration.

In fact, I thought that one argument against tau was that the standard normal distribution had a single sqrt(pi) rather than sqrt(2pi), but nope! It does have a 2pi. I guess the integral from -infinity to infinity of e^(-x^2) has the sqrt(pi)...

So anyway, I'm a math professor who loves tau. I'm not at all a fan of pi day, and I won't stand for this pi propaganda merely because "well then we can have pie on pi day". Lame. I spend pi day in my math tutoring center explaining why tau is superior. 

[Shatter He/Him]

I like τ and π. I'm not an ultra mathy guy, so I just decide which one to use and stick with it.

[Keteᛕ He/Him/His]

The formula for the area of a circle is A = pi r^2, compared to A = (tau r^2)/2...

pi is also much older

[KaladinsSenseOfHumourSpren He/Him]

7 minutes ago, Keteᛕ said:

The formula for the area of a circle is A = pi r^2, compared to A = (tau r^2)/2...

That is one equation, when tau makes basically everything else easier. Do you do trig?

Also, as Chaos said, it aligns well with the kinetic energy formula.

8 minutes ago, Keteᛕ said:

pi is also much older

That is not a good reason... geocentrism is way older than anything else...

[Usseewa ✾ She♡They ✾]

13 hours ago, KaladinsSenseOfHumourSpren said:

That is not a good reason... geocentrism is way older than anything else...

aggree

 

makes me question everything we think we know, and believe  

[KaladinsSenseOfHumourSpren He/Him]

9 hours ago, Usseewa said:

 

makes me question everything we think we know, and believe  

Aaaand that is how science happens  

[Shatter He/Him]

On 6/15/2026 at 6:03 PM, KaladinsSenseOfHumourSpren said:

That is one equation, when tau makes basically everything else easier. Do you do trig?

Also, as Chaos said, it aligns well with the kinetic energy formula.

That is not a good reason... geocentrism is way older than anything else...

  Technically, heliocentrism is almost as old. It's from 250 BCE, and geocentrism is from 380 BCE. 

At least according to recorded history.

I also see some bias in the pinned tag...

[Chaos he/him]

On 6/16/2026 at 4:53 AM, Usseewa said:

makes me question everything we think we know, and believe  

Good! We should question everything, and discard anything that doesn't have a good reason to believe. 

[Through the Living Wrath he/him]

You know guys, the tau that can be told is not the eternal τ.

As stated in the τ Te Ching

Edited June 17 by Through the Living Wrath

[KaladinsSenseOfHumourSpren He/Him]

22 hours ago, Shatter said:

I also see some bias in the pinned tag...

Also tau supporters, I found that online, there weren't any good tools to help memorise tau, so I made one!

https://k-sauce.github.io/tau_memoriser/index.html

I tried making it as fast as possible, so the UI isn't that great. It also doesn't work on mobile because you need to type the digits.

Also, I should've included this in the OP, but here's the tau manifesto: https://www.tauday.com/tau-manifesto

Edited June 18 by KaladinsSenseOfHumourSpren

[Just A Silvereye he/him/il/lui]

Well, I have been using pi forever, and I don't like changing stuff.

It logically follows that tau is heresy and all of you should be burned at the stake, for I shall not admit that one prefers doing things differently of me.

[DrPhysics he/him]

On 6/14/2026 at 5:44 PM, Chaos said:

A = 1/2 tau*r^2 is very symmetric with the kinetic energy formula. That 1/2 should be there anyway, due to integration.

@ChaosI'm going to call you out on this one (I'm a physics professor). If that's your justification, then volume of a sphere would be 1/6 tau r^3, not 2/3 tau r^3

Area integrals don't need to be symmetric with path integrals. (Please note tone of joking/sarcasm)

And solutions to the wave equation are much more satisfying to write as sin(n pi x/L). Who would want sin(n tau x/(2L))? That's a whole other constant I need to track through separation of variables.

Also, if we use tau for 2pi, what am I going to call torque, time constants, and shear stress?

Edited June 19 by DrPhysics
Spelling

[KaladinsSenseOfHumourSpren He/Him]

Happy Tau Day y'all  

[Through the Living Wrath he/him]

Not quite yet for me…