How to Create an Infinite Loop Symbol with Illustrator
Don't try to do this with the Pen Tool!
This tutorial will teach you how to take a basic circle shape and use Illustrator to manipulate, duplicate and layer it step by step to build a perfect infinite loop and also create the illusion of depth.
Launch Illustrator and create a new RGB document (800 x 520 px).
Draw a large rectangle that fills the artboard to use as a background layer. Set the fill to #2D2629 and the stroke to none.
Use the Ellipse tool to draw a 125 x 125 px circle in the center of the canvas with a 50pt #D73562 stroke and no fill.
Use the Convert Anchor Point tool and click once on the right-most point of the circle.
Highlight the same point with the Direct Selection Tool and use the arrow keys to nudge it 20 pixels to the right.
Add a new vertical guide as shown below at X:450 px.
Select the top anchor point and drag the right handle to meet the vertical guide.
Repeat for the bottom anchor point, they should both snap to the guide if you have Smart Guides (CMD+U) enabled.
Set the reference point for the shape to the right and use Flip Horizontal from the Transform Panel
Select both shapes and re-align them to the center of the artboard.
Use the Direct Selection tool and hold down the Shift key to select the two line segments show in the image below (just the segments not the anchor points).
Copy and paste the two segments to duplicate them.
Group the segments and double click them to enter Isolate Mode. Then highlight the middle points and Join (CTRL+J or CMD+J) them to create a complete line.
Exit Isolation Mode and duplicate the right hand side shape in place (you can change the stroke color to black to differentiate it from the original).
Enter Isolation Mode again for the duplicated shape and delete the two points shown.
You should be left with just this segment:
Select the black segment and also the middle segment, convert their strokes to outlines then make a copy of the middle segment (because we'll need to reuse it for the other side) and subtract one of the middle segments from the black segment using Pathfinder.
This should be the result:
Repeat this process for the other side, start by duplicating the left-most shape and changing it's fill to black.
Then enter Isolation Mode and delete the two points shown.
Use the remaining copy of the middle segment to subtract from the black segment.
You should be left with this:
Apply a gradient fill to the right-most black shape. Both stops are the same color as the background, but one stop is 100% opacity and the other is 0% opacity. The angle should be around 35° but you can also use your eye.
Apply the same gradient to other side and flip the direction.
Result & Conclusion
Here is the result:
I also loaded the image into Photoshop and applied some very subtle grunge effects for a finishing touch:
There are lots of different ways to manipulate shapes in Illustrator, and sometimes seemingly complex shapes can be simpler than they seem. To draw this shape manually with the Pen tool would be extremely frustrating, but by starting with a basic circle we can manipulate and build the infinite loop with perfect dimensions.