CarpentryPro — Angle Calculator & AI Assistant

Miter Angle Calculator

How to use: Select your joint type and enter the corner angle. The calculator gives you the exact blade setting for each piece.

Joint Type

Corner Angle (degrees)

Number of Sides (polygon)

Blade Direction

Calculation Results

Miter Angle (each piece)—

Saw Blade Setting—

Complementary Angle—

Joint Note—

Bevel Angle Calculator

Desired Slope (deg)

Board Thickness (in)

Roof Pitch (X:12)

Bevel Results

Bevel Angle—

From Roof Pitch—

Vertical Drop per Foot—

Rise Over Run—

Common Miter Cuts

45 deg

Square Corner Frames

The workhorse cut. Used for picture frames, window casings, door frames, and baseboards at 90 degrees. Both pieces get the same cut.

22.5 deg

Octagon / 8-Sided

Used for octagonal tables, gazebo frames, or any 8-sided shape. Each piece gets a 22.5 deg cut on both ends.

30 deg

Hexagon Frames

Six-sided projects like hex shelves, planters, or decorative panels. Each of 6 pieces gets 30 deg on both ends.

Outside Corners

Walls Not 90 deg?

Measure actual angle with a digital angle finder. Divide by 2 for your miter setting. Most older homes vary 88 to 94 degrees.

Inside Corners

Cope, Don't Miter

For inside baseboard and crown corners, professionals cope rather than miter. Coped joints hold better as wood expands.

Scarf Joint

Joining Long Runs

When baseboards span longer than one board, join mid-wall with two 22.5 deg cuts. Always land over a stud and glue it.

Miter Angle = (Interior Corner Angle) divided by 2

For Polygon: Miter Angle = 90 minus (180 divided by Number of Sides)

Compound Cut Calculator

Crown Spring Angle

Wall Corner Angle

Compound Cut Settings

Miter Saw Angle—

Bevel Saw Angle—

Molding Position—

Corner Type—

Master Craftsman Tips

Measure

Measure Twice, Cut Once

Always measure your actual corner angle with a digital angle finder. Never assume it is exactly 90 degrees. Most walls are off by 1 to 3 degrees.

Test Cuts

Always Cut Scrap First

Verify your angle on a scrap piece before cutting good stock. Hold both pieces together and check with a square.

Long Stock

Support Long Pieces

Use roller stands at both ends for pieces over 4 feet. Unsupported boards flex and cause inaccurate cuts and kickback.

Blade Kerf

Account for Kerf

Your blade removes about 1/8 inch of material. Always cut on the waste side of your line and sneak up on final dimensions.

Stair Math

Stair Stringer Layout

OSHA: riser 7 to 7.75 inches, tread 10 to 11 inches. Stringer angle = arctan(total rise divided by total run).

Blade Choice

Right Blade for Clean Cuts

Finish work: 80 to 100 tooth blade. Framing: 24 to 40 tooth. More teeth equals smoother cut, slower feed.

Polygon Miter Angle Reference

Sides	Shape	Corner Angle	Miter Cut Each	Common Use
3	Triangle	60 deg	30 deg	Decorative shelves
4	Square	90 deg	45 deg	Frames, boxes, baseboards
6	Hexagon	120 deg	30 deg	Hex shelves, planters
8	Octagon	135 deg	22.5 deg	Gazebos, tables, mirrors
12	Dodecagon	150 deg	15 deg	Clock faces, barrel tops

Roof Pitches to Bevel Angles

Pitch (X:12)	Angle	Notes
4:12	18.4 deg	Min. for asphalt shingles
6:12	26.6 deg	Very common residential
8:12	33.7 deg	Steep residential
12:12	45.0 deg	Equal rise/run

Lumber Nominal vs Actual Sizes

Nominal	Actual	Common Use
2x4	1-1/2 x 3-1/2 in	Framing studs
2x6	1-1/2 x 5-1/2 in	Rafters, headers
2x8	1-1/2 x 7-1/4 in	Joists, beams
2x10	1-1/2 x 9-1/4 in	Floor joists
2x12	1-1/2 x 11-1/4 in	Stair stringers
4x4	3-1/2 x 3-1/2 in	Posts, deck

Quick Stair Calculator

Total Rise (in)

Total Run (in)

Stair Results

Number of Risers—

Riser Height—

Tread Depth—

Stringer Angle—

Stringer Length—

🔒 Unlock AI CarpentryBot + full access

$4 / This Tool $12 / All Tools

🧹

CarpentryBot

AI Master Craftsman

🧹 Hey! I'm CarpentryBot — your AI master craftsman. Ask me anything about angle cuts, miter settings, crown molding, roof rafters, stair stringers, joinery, and tool tips. What are you building?

🔒 AI Advice is Premium

Unlock CarpentryBot AI

🪵 CarpentryPro