Miter Angle Calculator
ConstructionFind the exact miter angle to cut pieces for any regular polygon frame, box, or planter. Enter the number of sides to get the precise saw angle instantly.
Reviewed by the thecalcu.com team · Last updated July 8, 2026
Miter Angle
What is a Miter Angle?
A Miter Angle Calculator determines the exact saw angle needed to cut pieces so that they join cleanly into a closed, regular polygon, whether that's a simple 4-sided picture frame, a hexagonal planter box, or an octagonal gazebo frame. The primary keyword here, miter angle calculator, addresses one of the most common questions in woodworking and DIY carpentry: what angle do I set my miter saw to for this shape?
The tool uses a single input, the number of sides in your target shape, and instantly returns the miter angle in degrees. This works because any regular polygon's exterior corner geometry follows a fixed mathematical relationship: 180 degrees divided evenly across the number of sides. No measuring, protractors, or angle charts are required, just enter the side count and cut.
Building a frame, a box, a planter, or a multi-sided structure, getting the miter angle right the first time avoids wasted material and mismatched joints, which is especially valuable when working with expensive hardwood or trim stock.
Why Use a Miter Angle Calculator?
Manually deriving miter angles from polygon geometry is easy to get wrong, especially for shapes beyond the common square frame. A Miter Angle Calculator removes the guesswork and the risk of a costly mis-cut, delivering the precise angle for any regular polygon from a triangle up to a 20-sided shape.
For DIY builders and hobbyist woodworkers, the calculator turns a project idea, "I want to build a hexagonal planter", into an actionable cut list in seconds, without needing to recall trigonometry from school. For professional carpenters and trim installers, it serves as a fast double-check before making a cut on expensive crown molding or custom millwork.
Pair this calculator with the Angle Cut Calculator for compound and rafter-style angle cuts, or the Rafter Length Calculator if your project involves roof framing rather than a flat frame or box.
Who Should Use This Calculator?
DIY woodworkers and hobbyists building picture frames, mirror frames, planter boxes, or decorative multi-sided shapes will find this the fastest way to get an accurate cut angle without consulting reference tables.
Professional carpenters and trim installers can use the calculator as a quick field reference when framing custom shapes, verifying crown molding corner angles, or laying out multi-sided structures like bay windows and octagonal decks.
Landscape and garden builders constructing hexagonal or octagonal raised beds, planters, or gazebo bases benefit from getting the correct angle before cutting pressure-treated lumber, which is costly to waste.
Students and hobby CNC or laser-cutting users working on polygon-based projects can use the tool to quickly verify joint angles before programming a cut path.
What Insights Does the Miter Angle Calculator Give You?
The calculator returns a single, focused output: Miter Angle, expressed in degrees, which is the exact angle to set on your miter saw's gauge for each cut end of every piece in your closed polygon.
This angle applies uniformly to every piece in a regular polygon, each of the pieces gets identical cuts at both ends, since a regular polygon has equal side lengths and equal corner angles throughout. For a 4-sided frame this is 45 degrees, for a 6-sided hexagon it's 30 degrees, and for a 12-sided shape it drops to 15 degrees.
Because the angle shrinks as the number of sides grows, the calculator also helps you sanity-check whether your saw can even achieve the required setting, most consumer miter saws have a practical minimum angle range, so very high side counts (16–20 sides) may require a specialty jig or a table saw sled instead.
How to use this Miter Angle calculator
Identify your target shape. Count how many sides your finished frame, box, or structure will have, a rectangle has 4, a hexagon has 6, an octagon has 8, and so on.
Enter the Number of Sides using the slider or number field, from a minimum of 3 (triangle) up to a maximum of 20 sides.
Read the Miter Angle result in the highlighted card, this is the angle in degrees to set on your miter saw for every cut in the project.
Set your saw to the calculated angle, and cut a pair of test scraps first to confirm the joint closes cleanly before cutting your final material.
Cut all pieces at the same angle on both ends, since a regular polygon uses identical miter cuts throughout, there is no need to alternate angles between pieces.
Dry-fit the full assembly before gluing or fastening, checking that all corners close without gaps.
Show formula & methodology ↓Show less ↑
Formula & Methodology
The calculator applies the standard regular-polygon miter geometry formula: > Miter Angle = 180° ÷ Number of Sides This works because the sum of a regular polygon's exterior angles always totals 360 degrees, split evenly across all corners, and the miter cut at each joint is half of that exterior angle contribution per piece, which simplifies to 180 divided by the number of sides for the angle set on a standard single-bevel miter saw. Worked examples: - 4 sides (square frame): 180 ÷ 4 = 45° - 6 sides (hexagon): 180 ÷ 6 = 30° - 8 sides (octagon): 180 ÷ 8 = 22.5° - 12 sides: 180 ÷ 12 = 15° This formula assumes a regular polygon, equal side lengths and equal interior angles. For irregular shapes or compound angles (where the frame or box also has sloped, non-vertical sides), an additional bevel angle calculation is required alongside the miter angle from this tool. Always verify with a test cut, since saw calibration can drift slightly from its printed scale over time.
Frequently Asked Questions