Compound Miter Calculator

Exact miter and bevel settings for crown, trim and splayed sides, at any corner

Project Details
Enter your measurements and requirements
Results
Calculated estimates for your project
Miter (saw swing)31.62°
Bevel (blade tilt)33.86°
Corner typeSquare (90°), inside

Turn these numbers into a build plan.

  • 90° corner
  • 31.62° miter
  • 33.86° bevel
Materials List
Recommended materials and quantities
Left pieceCeiling edge against the fence. Swing the miter right. Blade tilted left. Keep the left end.
Right pieceWall edge against the fence. Swing the miter left. Blade tilted left. Keep the left end.

Your room's corner list

Rooms have 4 to 8 corners and few are exactly 90°. Add each one so you have every saw setting on one sheet.

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Project plan · built from your numbers

90° crown molding corner, flat cut

Cut crown molding lying flat on the saw for a 90 degree corner: miter 31.62° and bevel 33.86° at a 38 degree spring angle. Includes test cuts on scrap before you touch the good stock.

Materials
$92
Time
1 afternoon
Level
Intermediate
7 steps 9 tools 6 materials
  1. 1

    Measure the actual corner

    Walls are rarely exact. Check the corner with an angle finder; the plan assumes 90°. If it reads differently, rerun the calculator with the real number.

    • Measure corner at ceiling height
    • Confirm molding spring angle (38 or 45 or 52)
    • Mark wall studs and ceiling joists
  2. 2

    Set the saw

    Lay the molding flat, back down on the table. Set miter to 31.62° and bevel to 33.86°. Lock both and make a test cut in scrap.

    • Miter 31.62°
    • Bevel 33.86°
    • Both locks tight
  3. 3

    Cut a test pair

    Cut a left and right piece from scrap about 12 in long. Remember the rule: for flat cuts, the top edge of the molding goes against the fence on one side and the bottom edge on the other, so label each piece.

    • Cut left piece
    • Flip and cut right piece
    • Label top edges
01 · Your numbers
Corner
90°
Miter
31.62°
Bevel
33.86°
Est. cost
$92
02 · The plan

7 steps · 9 tools · 6 materials

4 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

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90° crown molding corner, flat cut

Finished in 1 afternoon · $92 DIY

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How to calculate compound miter angles

  1. Measure the corner. Read the real wall angle with a digital angle finder or a bevel gauge. Walls are rarely exactly 90°, so measure every corner.
  2. Find the spring angle. Hold the crown in a framing square, back flat against both legs. The two angles it makes are its spring pair: 52/38 crown has a 38° spring angle, 45/45 crown a 45° one.
  3. Set the miter. Lay the crown flat, back down on the table, and swing the miter to the calculated angle. The dial reads from 0, which is a square crosscut.
  4. Set the bevel. Tilt the blade to the calculated bevel and lock both. A single-bevel saw tilts left, so the cut cards above tell you which edge goes on the fence for each piece.
  5. Test cut. Cut a left and right piece from scrap, hold them in the corner, and adjust by half a degree until the joint closes.

The formula for crown cut flat, with spring angle S and wall corner C: miter = atan(sin S / tan(C/2)) and bevel = asin(cos S x cos(C/2)). For a 135° bay window corner with 38° crown, C/2 is 67.5°, so the miter is atan(0.616 / 2.414) = 14.3° and the bevel is asin(0.788 x 0.383) = 17.6°. For splayed sides, with N sides tilted T from vertical: miter = atan(sin T x tan(180/N)) and bevel = asin(cos T x sin(180/N)).

The miter dial reads from 0 (a square crosscut), not from 90, which is why a 90° corner is 31.6° and not 58.4°. Also spelled compound mitre in the UK. Need to know how much crown to buy? Use the crown molding calculator; for flat casing and baseboard footage, the trim calculator. Hanging it? Follow the crown molding installation guide and check your profile in the trim profiles cheat sheet.

Compound miter angle chart

Crown cut flat on the table. Inside wall corner in degrees; 90 is a square corner.

Corner38° miter38° bevel45° miter45° bevel30° miter30° bevel
60°46.8443.0350.7737.7640.8948.59
62.5°45.4142.3549.3637.1939.4947.76
65°44.0241.6547.9836.6138.1346.92
67.5°42.6640.9446.6236.0136.8146.06
70°41.3240.2045.2835.4035.5345.19
72.5°40.0239.4643.9634.7734.2944.30
75°38.7438.6942.6634.1233.0943.40
77.5°37.4937.9241.3833.4731.9242.49
80°36.2737.1340.1232.8030.7941.56
82.5°35.0736.3338.8832.1229.6940.63
85°33.9035.5237.6631.4228.6239.68
87.5°32.7534.7036.4530.7227.5838.73
90°31.6233.8635.2630.0026.5737.76
92.5°30.5133.0234.0929.2725.5836.79
95°29.4332.1732.9428.5424.6235.81
97.5°28.3731.3031.8027.7923.6834.82
100°27.3230.4330.6827.0322.7633.83
102.5°26.2929.5529.5826.2721.8732.82
105°25.2928.6728.4825.5020.9931.82
107.5°24.3027.7727.4124.7220.1330.80
110°23.3226.8726.3423.9319.3029.78
112.5°22.3625.9625.2923.1318.4728.76
115°21.4225.0524.2522.3317.6727.73
117.5°20.4924.1323.2221.5216.8826.70
120°19.5723.2022.2120.7016.1025.66
122.5°18.6622.2721.2019.8815.3424.62
125°17.7721.3420.2119.0614.5923.57
127.5°16.8920.4019.2218.2213.8522.52
130°16.0219.4518.2517.3913.1221.47
132.5°15.1618.5017.2816.5512.4120.41
135°14.3117.5516.3215.7011.7019.35
137.5°13.4616.6015.3814.8511.0018.29
140°12.6315.6414.4314.0010.3117.23
142.5°11.8014.6713.5013.149.6316.16
145°10.9913.7112.5712.288.9615.09
147.5°10.1712.7411.6511.418.2914.02
150°9.3711.7710.7310.557.6312.95
152.5°8.5710.809.829.686.9811.88
155°7.779.828.918.806.3310.80
157.5°6.988.848.017.935.689.73
160°6.207.867.117.055.048.65
162.5°5.416.886.216.184.407.57
165°4.635.905.325.303.776.49
167.5°3.864.924.434.423.135.41
170°3.083.943.543.532.504.33
172.5°2.312.952.652.651.883.25
175°1.541.971.771.771.252.16
177.5°0.770.980.880.880.631.08

Compound miter FAQ

What does 38/52 mean on crown molding?

The two numbers are the angles the back of the crown makes with the wall and the ceiling when it is installed. They always add up to 90. For 52/38 crown, enter 38° as the spring angle; for 45/45 crown, enter 45.

What are the compound miter angles for a 90 degree corner?

For 52/38 crown cut flat: miter 31.62° and bevel 33.86°. For 45/45 crown: miter 35.26° and bevel 30.00°. Most saws have detents at 31.6 and 33.9 for exactly this cut.

What angle do I cut crown for a 135 degree corner?

For 52/38 crown cut flat on a 135° corner (a bay window or a 45° wall jog): miter 14.31° and bevel 17.56°. Cut nested upside down, it is a plain 22.5° miter.

Can I cut crown nested instead?

Yes. Set the crown upside down with the ceiling edge on the table and the wall edge on the fence, at its installed angle, then cut a plain miter of 90 minus half the corner: 45° for a 90° corner. No bevel. You need a saw tall enough for the crown.

What miter do I cut for baseboard at a 135 degree corner?

22.5° on each piece, which is 90 minus half the corner. Baseboard has no spring angle, so there is no bevel. Pick the flat trim mode above.

Why are my crown joints open at the top?

Usually the corner is not the angle you assumed, or the crown is not seated at its true spring angle on the wall. Measure the corner, re-run the numbers, and adjust the bevel half a degree at a time for gaps at the top or bottom, the miter for gaps on the face.

Do I need a dual-bevel saw?

No. A single-bevel compound miter saw cuts every piece; you just flip which edge goes against the fence. A dual-bevel saw saves the flipping. A sliding saw helps with wide crown.

What is the difference between a compound miter and a compound angle?

A compound miter is a cut with both a miter and a bevel, like crown at a corner. Compound angle usually means the same thing for splayed sides, such as planters and hoppers, where each side leans out. This calculator does both.

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Plan the whole project

Save every corner's saw setting in one place

Build the room's corner list above, then save it: each corner's miter and bevel, the crown per wall, and a checklist you can tick off at the saw on your phone. The calculators and cheat sheets stay free, no account required.

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