Crown sits on the wall and the ceiling at once, so a square room is not a 45° miter. Enter the spring angle and the wall corner. This returns the nested compound miter and bevel. Live, in the browser. The two numbers are the joint — not a left/right saw setup.
Crown sits on the wall and the ceiling at once, so a square room is not a 45° miter.
Use it for any corner that is not a plain 90° — bay windows, 135° corners, rooms that are out of square — or when your saw’s crown detents do not match your molding. Measure the corner with an angle finder, read the spring angle off the molding (38° and 45° are the common ones), and set the miter and bevel the page gives to cut the crown lying flat on the saw table.
Nested crown is a compound joint: the stick is tilted by the spring angle, and the wall turns by the corner. The cut therefore has both a miter (swing in plan) and a bevel (tilt). A 90° corner with real spring is not 45° and 0°. That pair is only the degenerate case of no spring at all — a flat board in the wall plane, which is a simple square miter, not crown.
Spring S on this page is the angle between the back of the molding and the wall. Common 52/38 crown is 38° off the wall and 52° off the ceiling. Enter 38, not 52. Swapping them swaps the two results. Ceiling spring is just 90° − S; it is shown on the calculator so you can check the stick.
miter = atan( sin(S) / tan(C ÷ 2) )
bevel = asin( cos(S) × cos(C ÷ 2) )
S = wall spring, C = included wall corner (folded to ≤ 180°).
Inside and outside of the same included angle share these magnitudes.
The shop check is nested 90° with 38° spring: 31.6° miter / 33.9° bevel (31.619° and 33.863° before rounding). An independent check using the same two lines matches this page. 45°/0° is not that check.
These are the compound angles of the joint. This page does not tell you which fence to use, which way to flip the stick, or whether to cut the crown nested against the fence or lying flat. That is a saw setup. Test a scrap from the same profile before you cut the room.
| Spring | Corner | Miter | Bevel |
|---|---|---|---|
| 38° | inside 90° | 31.62° | 33.86° |
| 45° | inside 90° | 35.26° | 30.00° |
| 52° | inside 90° | 38.24° | 25.81° |
| 38° | outside 90° (or 270° folded) | 31.62° | 33.86° |
| 38° | 135° bay | 14.31° | 17.55° |
| 38° | 85° (out of square) | 33.90° | 35.52° |
| 38° | 95° (out of square) | 29.43° | 32.17° |
| 0° | 90° | 0.00° | 45.00° |
Those eight rows come from atan(sin(S)/tan(C/2)) and asin(cos(S)×cos(C/2)). The first row is the usual shop check — 38° wall spring on a square inside corner. Rounding to one decimal is 31.6° and 33.9°. Spring 0 on a 90° corner is a 45° cut with the other axis at 0: a flat board, not crown. A carpenter still calls that a 45° miter with the blade square.
Because the stick is tilted. A simple 45° miter with no bevel only closes if the workpiece lies in the wall plane (spring 0). Nested crown has spring, so both the plan swing and the blade tilt move. For 38° spring the square-corner pair is 31.6° miter and 33.9° bevel, not 45/0.
Wall. Measure the back of the molding against the wall, or nest the flats in a square and read the wall-side angle. 52/38 crown is 38° on the wall and 52° on the ceiling — type 38. 38/52 crown is the other way around: type 52. The two results swap if you enter the ceiling angle by mistake. Ceiling spring on the calculator is 90° minus what you typed, as a check.
Not the magnitudes, for the same included angle. A square outside corner is still a 90° turn; the joint just closes the other way. Enter 90° and pick Outside. If you measured the reflex interior (270°), this page folds it to 90° and the miter/bevel stay 31.6° / 33.9° at 38° spring. Left vs right, ceiling-side long vs short, is a saw setup and is out of scope.
The actual included angle, not 90. Two scraps butted into the corner, or a protractor, beat hoping the drywall is square. A couple of degrees off a square room already moves both numbers — 38° spring at 85° is 33.9° miter / 35.5° bevel; at 95° it is 29.4° / 32.2°. Cut the corner you have.
Often, on wood that will move. Coping uses a square-cut first piece and a scribed second piece; it is a finish, not a different spring. This calculator still gives the compound pair if you are mitering both sides (MDF, stable paint-grade, or an outside corner). It is not a coping jig and not a scribing tutorial.
Enter 135. At 38° spring that is 14.31° miter and 17.55° bevel. At 45° spring, 16.32° and 15.70°. Do not bisect 135 by hand and call it 67.5° on the saw — that ignores spring the same way 45° ignores it on a square room.
No. It does not choose nested-against-the-fence versus lying flat, left versus right, upside-down versus right-side-up, or which way the bevel tilts on your particular saw scale. Those are handling. The calculator is the two compound angles of the joint. Make a test cut on scrap from the same profile and read the fit, not the internet.