Compound Miter Angle For a 8 Sided Planter 10 Degree Slope
Miter 22.19° / Bevel 3.81°
- 8 sides
- Slope from vertical: 10°
Methodderived from the panel face-normal geometry of a regular 8-sided frustum — see /tools/angle-calculator/ for the full derivation.
Slope is measured from the HORIZONTAL here (0° = flat frame) — some published tables measure tilt from the vertical instead, which gives the same physical cut with different-looking numbers. Confirm which axis your saw calls which before cutting a test piece.
An 8-sided planter box with sides sloped 10° needs a 22.19° miter and a 3.81° bevel — the shallowest slope of the four planter examples on this site, deliberately paired with the largest side count.
Why this one specifically
Octagonal planters tend to be built bigger than hexagonal ones — they're the shape behind large raised-bed garden kits and whiskey-barrel-style planters — and a wide, tall octagon with a steep flare would push its top opening dramatically wider than its base, using far more material than the design needs. Dropping the slope to 10° keeps the bevel angle under 4°, which is nearly a flat cut, so eight separate panels stay close to true rectangles rather than tapered trapezoids, saving both material and setup fuss across all eight glue-ups.
What moves the number
A quick note on which zero this site uses, because it changes how the number reads: a plain, unflared octagon is 0° here, and the figure grows as the panels lean outward from that baseline — several printed compound-angle references instead count the same lean starting from vertical, so the two won't share a scale even when they agree about the physical cut. Because both the miter and bevel depend on side count and slope together, cutting a test piece at these exact settings before committing full-size stock is worth the five minutes it takes.