What miter and bevel for crown molding on a 90° inside corner?
For standard 52/38 crown (a 38° spring angle) in a 90° inside corner, lay the crown flat and set the miter to 31.6 degrees and the bevel to 33.9 degrees. Cut it nested upside down instead and it is a plain miter of 45 degrees with the blade square.
How to work it out
- miter = atan(sin 38° ÷ tan(90° ÷ 2)) = atan(0.616 ÷ 1) = 31.6 degrees
- bevel = asin(cos 38° × cos(90° ÷ 2)) = asin(0.788 × 0.707) = 33.9 degrees
- Nested upside down: (180° − 90°) ÷ 2 = 45 degrees with the blade square
This is the corner in almost every room, and the numbers most saws mark with a detent. The hard part is not the angle but keeping the two pieces straight: the left and right pieces of an inside corner are mirror images, and each method puts a different edge against the fence.
Adjust for your project
- Miter angle — crown nested upside down (bevel 0°)
- 45 degrees
- Left-hand piece (as you face the corner)
- Lying flat (blade tilted left 33.9°): top edge against the fence, table swung right 31.6°, keep the left end. Nested: swing right 45°, keep the right side.
- Right-hand piece (as you face the corner)
- Lying flat (blade tilted left 33.9°): bottom edge against the fence, table swung left 31.6°, keep the left end. Nested: swing left 45°, keep the left side.
- Inside corner: many carpenters cope it instead — run the first piece square into the corner, cut the second nested at the miter above, then back-cut along the profile line with a coping saw. The coped piece rides over small wall errors.
A 90° inside corner by spring angle
| Spring angle | Miter (table) angle — crown lying flat | Blade bevel — crown lying flat | Miter angle — crown nested upside down (bevel 0°) |
|---|---|---|---|
| 38 | 31.6 degrees | 33.9 degrees | 45 degrees |
| 45 | 35.3 degrees | 30 degrees | 45 degrees |
| 52 | 38.2 degrees | 25.8 degrees | 45 degrees |
What to know about crown on a 90° inside corner
The usual mistake here is a gap at the bottom or top of the joint that looks like a bad angle but is really a piece cut the wrong way round. Lying flat, the left-hand piece goes top edge to the fence and the right-hand piece bottom edge to the fence — the reverse of what feels natural. Nested, the problem is the crown sliding down the fence during the cut, so the spring angle changes and the joint opens at the face. Clamp a stop strip to the table and hold the piece firmly.
Check the corner before blaming the saw. Inside corners collect joint compound, so the wall often meets at 91° or 92° and bows out near the ceiling. If the test pair closes at the top but gaps at the bottom, the corner is off square: measure it at crown height and enter the real reading.
For an inside corner, many trim carpenters skip the miter on one piece and cope it instead — cut the first piece square into the corner, then cut the second piece nested at 45° and back-cut along the profile line with a coping saw. The coped piece rides over small wall errors, and a coped joint does not open as the wood shrinks in winter.
A bay window is the next corner most people meet; its angles are on Crown molding angles for a 135° bay window corner.
Different size? Use the full Crown Molding Calculator.
What you’ll need
- Digital angle finderBudget price
Reads angles to a tenth of a degree — blade-to-fence, blade tilt and existing corners — so saw settings match the calculator.
See options on Amazon (opens in a new tab) - Compound miter sawPremium price
Fast, repeatable crosscuts, miters and bevels for trim, frames and cut lists. A sliding model handles wider boards.
See options on Amazon (opens in a new tab) - 18-gauge brad nailerMid-range price
Fixes trim, battens and moulding with small nails that are easy to fill. Cordless models skip the compressor and hose.
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Frequently asked questions
Is 52/38 crown the same thing as 38° spring crown?
Yes. The back of 52/38 crown meets the ceiling at 52° and the wall at 38°, and the spring angle is measured from the wall, so it is 38°. Crown labelled 38/52 sits flatter, reaching further along the ceiling than down the wall — it is uncommon, so measure it in a framing square before trusting the label.
Which edge of the crown goes against the fence for a nested cut?
The edge that touches the wall, with the ceiling edge down on the saw table. For the left-hand piece of an inside corner, swing the table right to 45° and keep the right side of the cut; for the right-hand piece, swing left and keep the left side.
What miter and bevel for 45/45 crown in a 90° inside corner?
Lying flat, a miter of 35.3 degrees and a bevel of 30 degrees. Nested upside down it is still 45 degrees — the nested miter depends only on the corner, not the crown.
How do I cut 52/38 crown for a 90° outside corner?
The angles do not change — a miter of 31.6 degrees and a bevel of 33.9 degrees lying flat, or 45 degrees nested — but the pieces are mirrored. Left-hand piece: Lying flat (blade tilted left 33.9°): bottom edge against the fence, table swung left 31.6°, keep the right end. Nested: swing left 45°, keep the right side. Right-hand piece: Lying flat (blade tilted left 33.9°): top edge against the fence, table swung right 31.6°, keep the right end. Nested: swing right 45°, keep the left side.
What if my 90° inside corner actually measures 92°?
Enter 92: lying flat the settings become a miter of 30.7 degrees and a bevel of 33.2 degrees, and nested each piece is 44 degrees. The change looks small on the saw scale, but cut at the 90° settings the joint can open visibly on wide crown.
Other common sizes
- Crown molding angles for a 135° bay window corner — 14.3 degrees
Sources
- DEWALT DWS715 12 in. compound miter saw instruction manual — Cutting Crown Molding (opens in a new tab) — 52°/38° crown profile, 31.6° miter and 33.9° bevel for a 90° corner, and the left/right cut charts for both methods.