Compound Miter Calculator
Calculate crown molding miter and bevel angles for cutting flat. Enter the wall corner and spring angle, then check the illustrated 38° crown example.
Quick answer. For crown cut flat, a 90° wall corner and 38° spring angle from the wall give approximately 31.62° miter and 33.86° bevel. These are angle magnitudes; the piece orientation determines the direction of each setting. See the method and references
Set up your calculation
An illustrative example is loaded. Replace its values with your measurements, costs or documented settings.
Calculation
Your result
- Saw miter magnitude
- 31.62 °
- Blade bevel magnitude
- 33.86 °
The quote handoff carries your inputs and assumptions. Only an explicit base cost is suggested as a quote cost; prices, rates and measurements remain planning notes.
Measure the two input angles first
Measure the wall corner
Use the included angle where the two walls meet. A square inside corner is 90°. Do not enter the saw-table miter setting here.
Measure spring from the wall
Read the crown’s installed angle from the wall, not the ceiling. Mark the wall and ceiling contact edges so that reference stays clear.
Identify the piece before cutting
Mark inside or outside corner, left or right piece, and the finished side to keep. Use your saw’s orientation chart and fit a scrap pair first.
Keep the result with the work
Copy or print the result with its measurements and assumptions. The quote handoff can retain these angles as planning notes; it does not treat degrees as a cost.
How it works
Miter = atan(sin(spring) ÷ tan(corner ÷ 2)). Bevel = asin(cos(spring) × cos(corner ÷ 2)). Spring is measured between the molding and wall.
- For crown molding held flat, with equal profiles on both sides of the corner. A 90° corner and 38° spring produce 31.62° miter and 33.86° bevel.
- These are angle magnitudes. Inside/outside corners and left/right pieces change direction and which edge faces the fence. Follow the saw’s crown-cut orientation chart and verify offcuts.
Why both crown angles change
Formula and units
- Miter = atan(sin(S) ÷ tan(C ÷ 2))
- Bevel = asin(cos(S) × cos(C ÷ 2))
C is the included wall corner; S is the crown spring angle measured from the wall. Evaluate trigonometric inputs consistently in degrees, or convert to radians and convert the final result back. These are the formulas used by this calculator.
| Wall corner | Spring from wall | Miter | Bevel |
|---|---|---|---|
| 88° | 38° | 32.52° | 34.53° |
| 90° | 38° | 31.62° | 33.86° |
| 92° | 38° | 30.73° | 33.19° |
| 90° | 45° | 35.26° | 30.00° |
DEWALT’s flat-cut crown guide covers 38°/52° and 45°/45° profiles and requires scrap checks [1]. Its familiar 38° profile chart prints 31.62° miter and 33.85° bevel; direct evaluation here rounds the bevel to 33.86°. That hundredth of a degree is not a promise of saw-setting precision.
A room corner that measures 92°
For 38° crown at an actual 92° included corner, the calculator gives about 30.73° miter and 33.19° bevel. Record the measured corner and the wall-reference spring angle. Label a matching scrap pair with the room-facing side and the end to keep, then follow your saw’s orientation chart before fitting the joint.
What your result means
- The joint is open
- Recheck the wall angle, spring reference and stock position before adjusting the calculated angles. A 38° wall reference is not the same input as 52° from the ceiling.
- The numbers look correct
- They specify magnitudes only. Inside/outside corners, left/right pieces and single/dual-bevel saws need the correct orientation [1].
Assumptions and limits
This method assumes equal crown profiles cut flat. It is not a formula for every compound joint, unequal spring angles or crown nested against a fence. Verify that the saw can make the required settings and that the molding is supported as its manual specifies.
Sources and content notes
- DEWALT: how to cut crown molding
Flat versus nested cutting, common crown profiles, setup orientation and the 90° reference settings.
Maintained by WoodWorkCalc · Reference content updated . Equations and worked values were checked against the calculator implementation. Scenarios are illustrative; they are not field-test records or independent technical certification.
Continue planning
Cut 38° crown for a 90° wall corner
| Input or step | Example value |
|---|---|
| Included wall corner | 90° |
| Spring angle measured from the wall | 38° |
| Miter magnitude | 31.62° |
| Bevel magnitude | 33.86° |
| Cutting position | Crown lying flat on the saw table |
These magnitudes match the calculator’s loaded example. They do not specify left/right settings or which offcut to keep. Use your saw’s crown orientation chart and test matching scrap before cutting the finished molding.
Common questions
Do I enter 38° or 52° for 38/52 crown?
Enter the angle between the installed crown and the wall. For a profile installed at 38° from the wall, enter 38°. Its angle from the ceiling is 52°; those inputs are not interchangeable.
Can I use these settings with crown nested against the fence?
No. These formulas are for cutting crown flat with both miter and bevel. Nested cutting uses a different setup; follow the saw manufacturer’s instructions.
Does this calculate every compound woodworking joint?
No. This tool covers equal-profile crown molding at a wall corner. Use the framing-angle calculator for flat frames and the bevel-angle calculator for a bevel from a measured offset.
What if my corner is not exactly 90°?
Measure the included wall angle and enter it. Keep the spring angle referenced to the wall, then confirm the joint on scrap with the intended left and right orientations.
Learn the method in the Academy
Follow the matching lesson or workshop reference before applying the result.
Use this in your project
Continue with the next measurement or cost, then keep the assumptions with your quote.
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