SawWise

Polygon frame calculator

Cut equal rails for a hexagon, octagon or other regular frame

Choose the number of sides and the outside measurement you actually care about. The calculator gives the mitre setting and both reference lengths for every identical rail.

Your measurements

Size the polygon rails

Target measurement

Saw mitre from square

30°

Cut 6 identical rails. Keep full angle precision for test cuts; small errors accumulate around the frame.

Long point

173.2mm

Short point

150.1mm

Outside across flats

300mm

Outside across points

346.4mm

Inside across flats

260mm

Net long-point stock

1039.2mm

6 equal sidesAcross flats: 300mmOne of 6 identical railsMitre from square30°Long: 173.2mmShort: 150.1mmStock: 20mm
6-sided regular frame with the selected target and one of 6 identical cut pieces shown.
Net stock excludes kerf and setup waste. Test the angle with scrap before cutting all the rails.

Across flats and across points

Across flats measures between two opposite parallel sides. Across points measures between opposite corners and is larger for the same polygon. For an odd number of sides there is no pair of opposite parallel sides in the everyday sense, but the calculator still reports the underlying apothem-based envelope.

Which rail length goes at the saw?

The long-point length is measured between the outside mitre tips. The short-point length is measured between the inside tips. Mark both on a test rail so the chosen stop or fence reference is unambiguous.

Mitre angle

The saw setting from a square crosscut is 180° ÷ number of sides. An octagon therefore uses 22.5° at every rail end; a hexagon uses 30°. Keep more precision than the saw scale displays when checking unusual side counts.

Why rings fail to close

Small angle errors accumulate around every joint. Straight, equal-width stock and identical rail lengths matter as much as the calculated angle. Cut test segments, assemble them without glue and correct the setup before processing all the finished stock.

Stock estimate

The reported stock is the sum of finished long-point lengths. Add kerf, end trimming, defects and setup waste. Alternating nested cuts can save material, but the safe sequence depends on the saw and how each segment is held.