Home Improvement Expert Danny Lipford

How to Find the Center of a Circle

By:

square pencil circle

Whether you’re drilling holes in a flower pot or dabbling in carpentry, finding the exact center of a circle can be a challenge. Here’s an easy solution for finding the center of a circle that will work with any project or material.

How to Find the Center

Remember high-school geometry? Yeah, me neither. But whether you know it or not, you’ll be using geometry for this simple task, specifically Thales’ Theorem and the idea that right angles always cut a circle through its diameter.

To find the center of a circle, all you need is a 90-degree angle and a straight edge. A framer’s square has both, but you can improvise with a piece of cardboard, paper, or whatever you have on hand, as long as the corners are 90 degrees.

Step 1

right angle on edge

Lay the square on top of the circle, with the right angle touching the edge. Don’t worry about positioning – the beauty of the theory is that it doesn’t matter.

Step 2

mark edges

Mark the circle where the sides of the square cross the edge of the circle.

Step 3

draw line straight edge

Using a straight edge (one side of the square works great), draw a line connecting the two marks.

Step 4

reposition square

Reposition the square so the right angle touches the edge in another spot, and repeat steps 1-3.

Step 5

x center

Now you have an “X” marking the center of your circle. Pretty easy, huh?



Please Leave a Comment

4 Comments on “How to Find the Center of a Circle”

You can follow comments to this article by subscribing to the RSS news feed with your favorite feed reader.

  1. LeRoy O. Lindquist Says:
    March 9th, 2011 at 6:35 am

    Thanks for your illustration of how to find the center of a circle. My wife makes baskets and uses wooden circle bases. Now I would like to know how to make a groove on the circle face one half inch wide and one eighth deep. This would be in a shape of a cross to place glued vertical boards. These boards are dividers within the weaved basket.
    Thanks again on the center finding illustration. Hope my question makes sense. Also is there an easy way to make wooden circles? I’m cutting them on a scroll saw and it is slow and not too accurate.

  2. Official Comment:

    Ben Erickson Says:
    March 9th, 2011 at 11:35 am

    Hi LeRoy,
    One method I’ve used to cut circles with a bandsaw is to make a jig with a plywood base that has a guide attached to the bottom which rides in the bandsaw miter slot. Put a nail sticking out of the plywood base at the circle radius from the saw blade. Drill a small hole the same size as the nail in the middle of the square circle blank, place the hole on the nail, move the jig into the blade, then rotate the blank 360 degrees to cut out the circle. A similiar jig can be made for a jigsaw or scroll saw, but it will be harder to set it up without a miter slot. I would use a router with a fence to cut the grooves on the circle face using the straight edge of the circle blank while it’s still square. Good luck with your project!

  3. Official Comment:

    Julie Day Says:
    March 9th, 2011 at 2:35 pm

    LeRoy, I don’t know if you can tell from the photos, but that’s a wooden basket bottom that my Dad made. He cut the circle with a band saw using a setup very similar to Ben’s suggestion above. Instead of a nail in the center, he used a machine screw that had been sharpened to a point. As for the groove, you could also use a table saw or radial arm saw with a dado blade. Good luck!

  4. dennisk Says:
    May 22nd, 2013 at 9:56 pm

    Excellent information:)

We want to hear from you! In addition to posting comments on articles and videos, you can also send your comments and questions to us on our contact page or at (800) 946-4420. While we can't answer them all, we may use your question on our Today's Homeowner radio or TV show, or online at todayshomeowner.com.

Click to check out all our great giveaways!