How to Construct an Octagon with a Compass

Last Updated: November 28, 2022

If you want to draw an octagon shape using your compass, you've come to the right place. In this article, we'll explain how you can easily draw a series of lines and points that will ultimately form an octagon. If you're ready to get started, scroll down!

1

Lay the sheet of paper on a flat surface.

Gather your materials and set up your work space. You will need:
- A mechanical compass with pencil
- A pencil eraser
- A ruler
- A spare pencil (recommended)

2

Draw a horizontal line across the middle of the sheet.

Make the line 9 inches long. For best results, use light pencil markings.

3

Find the midway point at 4.5 inches.

Mark the midpoint and call it "A." This will be the center of your octagon.

4

Put your compass next to the ruler.

Measure the width of the pencil tip and the compass needle. Adjust it to 3 inches.

5

Put the compass needle on point A and the pencil tip on the line.

6

Use one hand to hold the compass handle.

Twist the compass handle to create a circle as shown. Be careful since the compass needle is sharp.

7

Find the 2 points where the line and circle intersect.

Label the first point on the left end "B." Label the second point on the right "C."

8

Put the compass needle on point C and the pencil on point A.

9

Twist counterclockwise to create an arc intersecting the circle.

10

Find the 2 points where the arc intersects the circle.

Call the uppermost intersection point "D" and the lowermost point "E."

11

Draw a vertical line segment to connect points D and E.

Use a pencil and ruler to draw the vertical line.

12

Find where the line segment DE intersects the line.

Call this point "F."

13

Put the compass needle on point F and the pencil on point A.

14

Twist your hand to create an arc intersecting line segment DE.

It should intersect at 2 points.

15

Label the intersection between points D and F point "G."

Label the intersection between F and E point "H". Then, place the ruler across the circle, lining it up next to points A and H.

16

Draw a diameter containing points A and H across the circle.

Make the diameter intersect the circle at 2 different points.

17

Label the upper point "I" and the lower point "J."

18

Align the ruler along points A and G.

Draw a diameter containing points A and G. Make sure the line intersects the circle at 2 more points. Label the 2 new intersections as follows.
- The upper right most intersection should be called point K.
- The lower left most intersection should be called point L.

19

Put the compass needle on point K and the pencil on point C.

20

Twist to make an arc intersecting the circle at a new point.

Call this new point M.

21

Put the compass needle on point J and the pencil tip on point C.

22

Twist counterclockwise to create an arc intersecting the circle at a new point.

Call this new point N.

23

Line up the ruler against the points B and I.

These points are near the upper left of the circle.

24

Connect the 2 points with a line to make line segment BI.

Repeat this step with the following points:
- Points I and M, creating line segment IM
- Points M and K, creating line segment MK
- Points K and C, creating line segment KC
- Points C and J, creating line segment CJ
- Points J and N, creating line segment JN
- Points N and L, creating line segment NL
- Finally points L and B, creating line segment LB

25

Look for your octagon.

Your octagon should now look like this. You have successfully created an octagon using a compass and a straightedge.
- As you can see, this is why its better to use light marks. Otherwise, your drawing may have this hard-to-erase marks left over.

Community Q&A

Question

Does it have to be 6 inches?

AnonymousSuperWriter

Community Answer

No, but it has to be somewhere proportionate. For example, you can also make the diameter 3 inches, meaning that you will have to reduce the other measurements by 50%.
Question

I need to construct the one with sides 5cm. How many inches will I use for the parameter?

Duck Woman Thing YT

Community Answer

1 inch is about 2 and a half centimeters, so 5 centimeters would be about 4 and a half inches.
Question

How to get eight equal sides?

Community Answer

Use a ruler! Rulers are helpful in many ways. You can also find shapes with 8 equal sides and copy it.