High school Design and Technology students are often asked to construct a regular octagon. This article illustrates two methods: using a compass and straight edge when given a circle; drawing an octagon from a square; and how to construct an octagon with set squares when given one side.
How to draw a regular octagon inside a circle
This method is suitable when you know the distance across the corners (AC).
- Use the AC distance to draw the circle (AC = diameter, so halving this gives you the radius)
- Draw vertical, horizontal and 45° lines through the centre of the circle
- Draw the octagon where these lines intersect the circle
Draw a regular octagon inside a square
This method is suitable when you know the distance across the flats (AF)
- Scribe arcs from the corner of the square that run through the centre of the square;
- Where these arcs intersect the square are the points on the octagon.
How to draw an octagon when given one side
- Draw the first side horizontally;
- Use 45/45° set squares to rule lines from each end;
- Step the side length along the line;
- Rule vertical lines;
- Repeat until the octagon is complete.
Amiria has a Bachelor of Architectural Studies, Bachelor of Architecture (First Class Honours) and a Graduate Diploma of Teaching. She is a CIE Accredited Art & Design and Design & Technology Coursework Assessor. Amiria now teaches Art, Design & Technology at ACG Parnell College.