A miter angle calculator determines the exact blade angle for your miter saw when building polygon frames, corner joints, or compound miter cuts. Getting the angles right before cutting saves material and ensures tight, gap-free joints on every project from picture frames to crown molding.
Set your miter saw to 45.00° and make 8 cuts (2 per piece) to build a 4-sided frame with perfect 90° corners.
Polygon Miter Angle Chart
| Shape | Sides | Corner Angle | Miter Angle |
|---|---|---|---|
| Triangle | 3 | 60° | 60.00° |
| Square / Rectangle | 4 | 90° | 45.00° |
| Pentagon | 5 | 108° | 36.00° |
| Hexagon | 6 | 120° | 30.00° |
| Heptagon | 7 | 128.57° | 25.71° |
| Octagon | 8 | 135° | 22.50° |
| Decagon | 10 | 144° | 18.00° |
| Dodecagon | 12 | 150° | 15.00° |
How to Use the Miter Angle Calculator
Whether you are building a hexagonal planter, framing a picture, or installing crown molding, getting the miter angle right is the difference between tight joints and frustrating gaps. This free calculator handles three common scenarios: polygon frames, corner joints, and compound miters.
Step 1: Choose Your Calculation Mode
Click one of the three tabs at the top of the calculator. Polygon Frame mode is for building regular shapes like hexagons, octagons, or picture frames. Corner Joint mode handles any two pieces meeting at a specific angle. Compound Miter mode is for cuts where both the miter and bevel must be set, such as crown molding or sloped frames.
Step 2: Enter Your Dimensions
In Polygon Frame mode, select a preset shape or type a custom number of sides. The miter angle is calculated instantly as 180 / n, where n is the number of sides. In Corner Joint mode, enter the desired corner angle. In Compound Miter mode, enter both the corner angle and the tilt or spring angle of the stock.
Step 3: Read Your Saw Settings
The result cards show the exact angle to set on your miter saw. For polygon and corner modes, you get a single miter angle. For compound miters, you get both the miter angle (table rotation) and the bevel angle (blade tilt). The visual diagram helps you confirm the geometry before making a cut.
Step 4: Use the Reference Table
The polygon miter angle chart below the calculator provides a quick reference for the most common shapes. Bookmark this page so you always have a miter angle reference on your phone or in the shop.
Understanding Compound Miters
Compound miter cuts are needed whenever stock is tilted away from vertical. The most common example is crown molding, which sits at a spring angle between the wall and ceiling. For a standard 38/52 crown (38 degrees from the ceiling), the tilt angle is approximately 33.9 degrees. The formulas used are: miter = arctan(sin(tilt) × tan(corner/2)) and bevel = arctan(cos(miter) × tan(tilt)). This calculator does the math so you can focus on making accurate cuts.
Frequently Asked Questions
Is this miter angle calculator free to use?
Yes, the miter angle calculator is completely free with no limits, no signup, and no account required. All calculations run locally in your browser, so you can use it as many times as you need.
Is my data safe when using this tool?
Absolutely. All calculations happen entirely in your browser using client-side JavaScript. Your measurements and project data are never sent to a server or stored anywhere. Everything stays on your device.
What miter angle do I need for a picture frame?
A standard picture frame is a four-sided rectangle, so you need a 45-degree miter angle on each piece. Set your miter saw to 45 degrees left or right, and each corner will close to a perfect 90-degree joint.
How do I calculate the miter angle for a hexagon?
For a regular hexagon (6 sides), divide 180 by the number of sides: 180 / 6 = 30 degrees. Set your miter saw to 30 degrees for each cut. This formula works for any regular polygon: miter angle = 180 / n, where n is the number of sides.
What is a compound miter cut?
A compound miter is a cut where the blade tilts (bevel angle) and the table turns (miter angle) at the same time. It is needed when stock is tilted relative to the joint, such as crown molding, sloped picture frames, or angled planter boxes.
What is the difference between a miter angle and a bevel angle?
A miter angle is the horizontal angle of the cut across the face of the board, controlled by rotating the saw table. A bevel angle is the vertical tilt of the blade through the thickness of the board. Simple miters use only the miter angle, while compound miters use both.
How do I cut an octagon on a miter saw?
For a regular octagon (8 sides), the miter angle is 180 / 8 = 22.5 degrees. Set your miter saw to 22.5 degrees and cut each piece with opposing miters on each end. All eight pieces will close into a perfect octagonal frame.
Can I use this calculator for crown molding?
Yes. Use the compound miter mode and enter the corner angle (usually 90 degrees for inside corners) and the spring angle or tilt of the molding. The calculator will give you both the miter and bevel settings for your saw.