I believe I'm noticing the same issue.

I have three rings of descending size and the two smaller ones should lay perfectly inside of it's larger parent ring. I had hoped using the pixel grid would fix the issue but I'm still unable to match the vector edges perfectly flush to the other. You'll notice in my image thin white lines where there are gaps between the rings. It's funny that the gap isn't all the way around, rather it becomes most apparent every 40 degrees.

The largest ring is 5.5" so the gaps are quite small, but as the design progresses it becomes more apparent.

I think for us to make this argument "properly", Marty, we need to take it to the W3C and somehow get them to revise the global standard of what <circle> is?
https://www.w3.org/

I think it's because <circle> is the same <circle> from 1963. https://en.wikipedia.org/wiki/Sketchpad
Nobody looked to make a better circle, because they could just do what everyone else did.
Copy, Paste, Circle.

I know the arguments though. Cross-Compatibility with other programs and all... and I KNOW a perfect circle cannot be drawn with quads, but at least we can achieve something as accurate as the confines of the program will allow now that its 2021? With all the AI additions and 3D rendering in photoshop..... we haven't upped the game in the way of circle accuracy?

My art is highly geometric and depends on perfect circles for perfect symmetry.

The imperfection of circles in Illustrator is highlighted when creating and rotating the "flower of life" design.

I am glad to see other people have noticed the same issue.

When working with a lot of circles, the imperfections/lopsidedness of them becomes very apparent with rotation of the work. My current piece should have perfect symmetry with every 60 degree rotation, but instead it stretches significantly (at least 5%).

I would also like to see an improvement to this flaw in the software.

By the way, the only 'pefrect' way I found to be working for me, is to use the Polygon tool with 360 'sides'.
The only downsides of it, is that it's still not a perfect cirlce, since it's still a polygon formed by 360 anchor points and when you duplicate and rotate it by 0.5° it still overlaps and won't fit perfectly, plus, it overloads the system and slows the computer while you use and adjust several similar shapes at a time.

Until today this issue still exists.
It's so frustrating to work with several circles in Illustrator and see how the lines just won't align around the artboard, especially when I try to make geometrical shapes, for example: the flower of life, as a background for some artwork...
All anchor points are placed fine, but it just misalign due to the imperfect circles of the software...

I really hope this thing will be fixed soon, as it affects lots of my works and designs.

I am using the rotate tool under Object > Transform > Rotate.

Within the Rotate dialogue box I type in a 60 degree rotation and I click the copy button.

I then use key command "Command - D" to continue copying the lines around a circle. See screen shots.

When I zoom in super close to the line to see if it is touching the outside of the circle the copy and pasted lines are either slightly inside or outside the circle.

Usually I would not care about a minimal inaccuracy like this but I am currently creating parts for a CNC router and I need it to be as accurate as possible. Is this a bug or am I using the tool incorrectly?

Anyone have a workaround to creating a perfect circle?

Equation for circle.
(x−h)² + (y−k)² = r²

Is there any way to leverage the actual math for a circle to draw a circle?

same here. every non-90°-rotation discovers the not perfect circle. will take a look at that dynamicshapes plugin, thank you Egor!

FWIW: The same thing with InDesign.
You cannot draw a perfect circle there as well.
The difference is minimal, but it is there.

Regards,
Uwe Laubender
( ACP )

Check my video and try it yourself. Amazing is it not?

---> draw a circle, set coordinates straight, copy and paste in place, rotate any degree from the middle, zoom in, tadaaaaaa... flawless accuracy adobe!

You will never have them perfect with Bezier curves.
Ellipse is always an approximation.
Let me cite this magnificent article — https://pomax.github.io/bezierinfo/:

“Circles and Bézier curves are very different beasts, and circles are infinitely easier to work with than Bézier curves. Their formula is much simpler, and they can be drawn more efficiently. But, sometimes you don't have the luxury of using circles, or ellipses, or arcs. Sometimes, all you have are Bézier curves. ... So how do you draw a circle, or an ellipse, or an arc?

You approximate.

We already know that Bézier curves cannot model all curves that we can think of, and this includes perfect circles, as well as ellipses, and their arc counterparts. However, we can certainly approximate them to a degree that is visually acceptable. Quadratic and cubic curves offer us different curvature control, so in order to approximate a circle we will first need to figure out what the error is if we try to approximate arcs of increasing degree with quadratic and cubic curves, and where the coordinates even lie.”

You can buy DynamicShapes plugin from AstuteGraphics — it allows you to create ellipses with more points — or use a script (http://shspage.com/aijs/en/#circle)