How to Find the Center of a Circle

You can find the center of a circle easily with a ruler! A little geometry lesson about chords and you'll be there.

[ajanki]

3 chords of EQUAL lengths ANYWHERE with in the circle. Take HALF of the line going through the circle and draw a perpendicular segment at the middle area of the circle and where the three PERPENDICULAR segments intersect is the CENTER of the circle ! U R A GENIUS SIR ! TY !

[davidlover]

1. Just 2 chords would be enough.
2. The chords need not be of same length.
3. Draw a perpendicular line from exact mid-point of these chords.
4. Point of intersection of perpendiculars would be centre.
5. Although not required, but a third chord and it's mid-point perpendicular would pass through the centre confirming the accuracy of the location of the centre.

[SenhorTudo]

ONE chord is enough! Draw it near the rim of the circle, but make it easily divisible by 2. Mark the centre of this chord. Place a square on this reference mark on the chord and draw a perpendicular line right across the circle. The middle of this line is the centre of the circle.

[MKahn]

Good method. Technically, you only need two chords, but it doesn't hurt to do the third one just to ensure you're accurate.

[lestersart]

There is an easier way. Take the point of that square and put it on the edge of that circle. Mark the points where the square ends pass over the edge of the circle. A line through that cuts that circle right in half. Now, you just need to move that point to another location and repeat the process. The single most important thing I ever learned in geometry class.

[kirkthiets]

The perpendicular bisector of a cord will also bisect the circle it was drawn in. You only need two bisected cords to point to the center that may be different lengths as well so long as the are bisected, or cut into equal parts.

[bootlegger]

Divider set to the radius of the circle. Point of divider to outside of circle and swing arc with pencil end marking the center. Repeat at several places of the outer circle. Much easier/accurate.

[beaustjohn]

hey man, believe this is the best and easiest way to find the center of a circle on youtube! i will be able to use this to solve many prob's in shop!

[siaripop]

From the looks of this description, all you would need is two cords, not three, the third only verifies the result of the first two!

[WhallonJesse]

My high school got rid of shop class. "Go to college or work at Thank you for posting this so people like myself can learn.

[AlejanroDelHierro]

If you already have a rectangle and set the right angle, then use the points where ends in the circle, and join them with line.
The cross section of 2 line of that kind is center of circle. Much simple, just a few seconds.

[WorkshopGreg]

Fantastic! So glad I found this - helped me immensely on a project I’m working on.

[erichandyauto]

You sir are the cat's meow. I'm making a shopvac filter retainer and need to drill a hole in the center of a paint can lid. Thank you for sharing.

[BloodSweatnBass]

You're the man thanks for sharing that. I read those sane instructions and had no idea what a "cord" was. That's a super helpful tip. You just saved me some cash $$.👍🏽👍🏽

[dunnekids]

Thank you from the bottom of my heart!

[jamescrydeman]

Two chords, parallel, equidistant from the circumference, the diagonals from where the chords intersect the circumference will cross in the middle.

[phpn]

The classic way to do this is to use a compass. Place the point of the compass at the edge of the circle and draw an arc that extends roughly beyong the centre of the circle. Keep the compass opened to this length and place its point againt, at what is roughly the opposite side and draw another arc. The two arcs will intersect at the diameter line. Repeat a third and fourth time to draw an intersecting diameter. The advantages of the compass method should be obvious.

[KGarvey]

I have a large circular canvas I want to do a painting on. This is going to be a big help.

[unclepunch]

Thanks! Your video was great and to the point.
Good math-ing.

[hizzyvoltaire]

I just stick a ruler on the circle and find its maximum, draw a line, then do the same when roughly perpendicular to the first line. where two diameters cross has to be the center.