Crown Molding Angle Calculator

How to figure out the angle for crown molding

You need two numbers: the crown’s spring angle and the angle of the wall corner. The calculator above turns them into the miter and bevel for cutting the crown flat on the saw; the formulas are below if you want to check it by hand.

Spring angle is how far the back of the molding leans away from the wall once it is installed. Most crown comes in one of two: 38° (the “52/38” type, whose back leans 38° off the wall and 52° off the ceiling, since the two add to 90°) or 45° (“45/45,” equal off both). Not all crown is one of these, so confirm yours. A square wall corner is 90°, though few real corners are.

miter = atan(sin S ÷ tan(C ÷ 2))
bevel = asin(cos S × cos(C ÷ 2))

S is the spring angle and C the wall corner angle, in degrees. Worked example, 38° crown in a 90° corner: sin 38° ÷ tan 45° = 0.6157, so the miter is 31.62°; cos 38° × cos 45° = 0.5572, so the bevel is 33.86°.

Crown molding settings for a 90-degree corner

For a square corner with the crown lying flat on the saw table, the settings come straight out of the formulas:

The same pair serves inside and outside corners of the same angle; what changes is the swing direction and which end of the cut you keep, which the calculator spells out for left and right pieces. DeWalt’s manual lists 31.62° and 33.9° for all four of those cuts.

The trigonometry is shared with the compound miter calculator, a separate tool that measures a side’s slope from horizontal rather than from the wall. A 38° crown leans 52° from horizontal, and four sides at a 52° slope there come out at 31.6° and 33.9° — the same pair — while 45° crown (the same 45° either way) matches four sides at 45°: 35.3° and 30.0°. For crown work itself, stay with the calculator above, which also does corners that aren’t square.

What is 33.9 on a miter saw?

It is the bevel setting for standard 38° crown cut flat in a square corner, used with a 31.6° miter. DeWalt’s manual for its DW708 sliding compound miter saw describes miter latch points at 31.6° and a mark on the bevel scale at 33.9° for that job; the unrounded numbers are 31.62° and 33.86°. If your crown is the 45° type, 33.9 is the wrong number — use 35.3° and 30.0°.

Does crown molding sit at a 45-degree angle?

Only 45/45 crown does. The more common 52/38 type sits at 38° from the wall (52° from the ceiling). The 45 that turns up in cutting instructions is normally the saw’s miter setting when the crown is nested against the fence for a 90° corner — a different number from the crown’s lean. If you cut flat instead, neither setting is 45: the pair is 31.6° and 33.9° for 38° crown.

Cut it flat on the saw or nested against the fence?

Flat: the crown lies on its back on the saw table and you set both a miter and a bevel — 31.6° and 33.9° for 38° crown in a 90° corner.

Nested: the crown stands upside down and tilted between the fence and the table, held at the angle it will have on the wall, with the fence playing the wall and the table the ceiling. The bevel stays at 0° and the miter is half the corner angle: 45° for a 90° corner, 46° for a 92° corner. DeWalt’s manual points out that with no bevel to set, corners that aren’t square are quick to adjust for; the catch is holding the crown at its spring angle, which is why the manual recommends a crown fence accessory.

Pick one method per job and stay with it. Each method has a size limit set by your saw, so check its manual for the largest crown it can cut flat and nested.

Crown molding angles when the wall isn’t 90 degrees

Measure the corner, put it in as C, and the formulas do the rest. Take a 92° corner with 38° crown: sin 38° ÷ tan 46° = 0.5945, so the miter is 30.73°; cos 38° × cos 46° = 0.5474, so the bevel is 33.19°. That is 0.89° less miter and 0.67° less bevel than the square-corner pair. SBE Builders’ published table for 38° crown lists the same figures for 88°, 90°, and 92° corners.

Inside or outside makes no difference to the numbers. The 45° column at 92° reads 34.3° / 29.4°. For a corner that isn’t listed, type it into the calculator above.

Can a 90-degree cut be made in crown molding?

Yes, two ways. A 90° wall corner is the standard case, with the settings in the table above. A plain square, 90° end cut is normal too: This Old House has you start an inside corner with a square-cut piece and butt a coped piece into it, so only the coped end needs the 45° miter-and-cope treatment and the first piece needs no compound angle at all.

Why crown needs two angles

Crown sits tilted between wall and ceiling, so a corner joint is a plane slicing through a tilted board — neither a pure miter nor a pure bevel reaches it. Cutting with the crown flat on the saw table means both adjustments at once: swing the table to the miter, tilt the blade to the bevel. The two identities above fall straight out of the geometry.

The order of operations that saves stock

• Measure every corner — never assume 90°.
• Cut a pair of test scraps per unique corner and check the fit on the wall.
• Mark orientation on the back of every piece before it leaves the saw — “ceiling side” arrows prevent the classic upside-down re-cut.
• Cope inside corners if you prefer: install one piece with a square-cut end and cope the mating piece into it. This Old House says coping makes a tighter fit than mitering an inside corner.