How to Construct an Octagon with a Compass

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.

  1. 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)
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2

Draw a horizontal line across the middle of the sheet.

  1. Make the line 9 inches long. For best results, use light pencil markings.
3

Find the midway point at 4.5 inches.

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    Mark the midpoint and call it "A." This will be the center of your octagon.
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4

Put your compass next to the ruler.

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    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.

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6

Use one hand to hold the compass handle.

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    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.

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    Label the first point on the left end "B." Label the second point on the right "C."
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8

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

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9

Twist counterclockwise to create an arc intersecting the circle.

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10

Find the 2 points where the arc intersects the circle.

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    Call the uppermost intersection point "D" and the lowermost point "E."
11

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

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    Use a pencil and ruler to draw the vertical line.
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12

Find where the line segment DE intersects the line.

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    Call this point "F."
13

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

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14

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

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    It should intersect at 2 points.
15

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

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    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.
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16

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

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    Make the diameter intersect the circle at 2 different points.
17

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

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18

Align the ruler along points A and G.

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    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.

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20

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

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    Call this new point M.
21

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

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22

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

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    Call this new point N.
23

Line up the ruler against the points B and I.

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    These points are near the upper left of the circle.
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24

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

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    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.

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    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.
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Community Q&A

  • Question
    Does it have to be 6 inches?
    AnonymousSuperWriter
    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
    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
    Community Answer
    Use a ruler! Rulers are helpful in many ways. You can also find shapes with 8 equal sides and copy it.
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Warnings

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Things You'll Need

  • A mechanical compass with pencil
  • A pencil eraser
  • A ruler
  • A spare pencil (recommended)


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About This Article

wikiHow is a “wiki,” similar to Wikipedia, which means that many of our articles are co-written by multiple authors. To create this article, volunteer authors worked to edit and improve it over time. This article has been viewed 34,058 times.
58 votes - 64%
Co-authors: 8
Updated: November 28, 2022
Views: 34,058
Categories: Drawing Shapes
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