How To Find the Center of a Circle

How To Find the Center of a Circle

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This is a handy trick that I learned for finding the center of a circle.

I made my girlfriend and I phone holders with steel discs for their bases. I had to drill and thread a center hole in each base for the articulating arms.

To figure out where I needed to the drill the center of the hole at, I used the method detailed below.

Materials needed:

  • Ruler
  • Sharpie marker

Step #1:

Make two equal length lines parallel to each other on the circle. In my case, I chose to use 3" long lines. So on the top of the circle, find where its width is 3" and make a straight line across. Then on the bottom of the circle, find where its width is 3" and make a straight line across there, too. You can use any width you'd like, as long as they're the same length.

center-disc-marking

Step #2:

Once you have two equal length lines parallel to one another, you can then connect them as pictured. You're making an X between the two lines.

center-disc-marking-2

Step #3:

You're all done. Where the two lines of the X meets will be the center of the circle.

center-disc-marking-3