Calculator · Geometry & layout
Polygon Side Length Calculator
The free Polygon Side Length Calculator answers one question: Side length for hexagons, octagons and more. Enter your numbers in inches or millimeters and the result updates instantly in your browser, with no sign-up and no app to install. Use it on your phone at the bench, then copy or print the result for your cut list.
Fit a regular polygon inside a circle of a given diameter (across the corners).
Polygon Side Length
- Side length
- 9.184″
- Across flats
- 22.173″
- Miter angle
- 22.5°
- Area
- 2.8 sq ft
Pro tools · unlock
Which other geometry & layout calculators help with this project?
- Hexagon Calculator — Across flats, across corners and area from side length.
- Golden Ratio Calculator — Pleasing proportions for furniture design.
- Diagonal & Squareness Calculator — Check a carcass or frame for square.
- Equal Spacing Calculator (Balusters, Slats) — Even gaps between slats, spindles or pegs.
What you'll need for this project
Tools
Screws & hardware
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Build it · Intermediate · 1 day
Download the complete plan with cut list and materials list (PDF)
Octagon Planter — Eight-sided planter with 22.5° beveled staves. Drawings, cut list with board-foot totals, hardware list and step-by-step instructions.