Crown Molding Calculator
Enter your wall run and your corner angle to get the miter and bevel to set on the saw, plus the linear feet and number of pieces to buy.
How crown molding is cut
Crown molding is not a flat piece of trim, so it cannot be cut with the saw table square and the blade upright. It goes onto the saw flat on its back, and the cut then has to happen in two planes at once: the table is swung across the molding and the blade is tilted over, because the molding leans back at its spring angle while the corner turns in the horizontal plane. Cut it that way and one pair of numbers fits every corner in the room.
Those two numbers are the miter and the bevel. The miter is the angle you swing the saw table to. The bevel is the tilt of the blade. They are not the same number, and that is the part that catches people out: the molding meets the wall at an angle and the corner turns, so the cut has to be tilted and swung at the same time. That is what a compound miter cut means.
For a square 90° corner, the two standard settings are:
- 38° crown — miter 31.6°, bevel 33.9°
- 45° crown — miter 35.3°, bevel 30°
There is a second way to do it, and plenty of carpenters prefer it: nest the molding in the saw instead, sitting at the angle it will sit on the wall — the edge that meets the ceiling flat on the saw table, the edge that meets the wall against the fence, no rocking. The cut is then a plain miter with no bevel at all, and at a square corner it is 45° whatever the spring angle, so it never needs the spring angle looked up. It is quicker to set up. It also needs a tall fence and a steadier hand, because the molding is standing on edge rather than lying flat, and the angles on this page are the flat cut, not that one.
Spring angle: 38° or 45°
The spring angle is the angle between the back of the molding and the wall when the molding is installed. Almost all crown sold today is one of two profiles:
| Profile size | Usual spring angle |
|---|---|
| 3¼ in | 45° |
| 3⅝ in | 38° |
| 5¼ in | 38° |
| 5½ in and larger | 45° |
Do not take that table as gospel — measure the molding you actually bought. Stand it in the corner it is going into and see how it sits, or set a bevel gauge against the back of the profile and read the spring angle off that. If it rocks against the wall and the ceiling, you have the wrong spring angle. The two figures are 4° apart, and a 4° error on the spring angle opens the joint on every corner in the room, not just one.
Miter and bevel for corner angles other than 90°
Walls are rarely exactly square, and bay windows, angled walls and older houses are nowhere near. Measure the corner with an angle finder and look it up here.
| Corner angle | Miter — 38° crown | Bevel — 38° crown | Miter — 45° crown | Bevel — 45° crown |
|---|---|---|---|---|
| 60° | 46.8° | 43.0° | 50.8° | 37.8° |
| 75° | 38.7° | 38.7° | 42.7° | 34.1° |
| 90° | 31.6° | 33.9° | 35.3° | 30.0° |
| 105° | 25.3° | 28.7° | 28.5° | 25.5° |
| 120° | 19.6° | 23.2° | 22.2° | 20.7° |
| 135° | 14.3° | 17.6° | 16.3° | 15.7° |
| 150° | 9.4° | 11.8° | 10.7° | 10.5° |
Two things to notice in that table. First, both angles fall as the corner opens up. A corner wider than square takes a shallower cut in both planes, and by 150° you are most of the way to a flat run. Second, the miter is the one that can run off the end of the saw. It passes 45° once the corner is tighter than about 63° in 38° crown, or about 71° in 45° crown, and most miter saws stop at 45°. The workaround is to cut the complement from the other side of zero: for the 50.8° miter that 45° crown takes at a 60° corner, set the saw to 39.2° on the other side and flip the workpiece against the fence. The cut is identical; you have just moved to the other side of the blade.
Corners, and why the length does not change
A mitered corner consumes no length. You measure each piece to the corner and cut the miter on the end of it, so the material you need is the length along the ceiling, corner to corner. Do not add anything for the corner itself.
Inside and outside corners take the same angles — a 90° inside corner and a 90° outside corner both miter at 31.6° with 38° crown. What changes is the direction: for an outside corner you swing the miter to the opposite side of zero and cut the other end of the stick. It is the same setup made the other way around, and it is the reason a room with outside corners is worth practising on scrap first.
Scarf joints: when a wall is longer than the stick
A 20 ft wall cannot be covered by a 12 ft stick, so the run has to be joined somewhere along its length. That joint is a scarf joint, and doing it well is most of what separates a clean job from a visible one:
- Cut it on an angle, not square. A 45° lap hides the joint inside the profile. A square butt joint shows a straight line across the face of the molding.
- Land it on something solid. A scarf joint must sit over a ceiling joist or a stud, because the two pieces have to be pulled tight to each other. Glue it and nail both sides.
- Put it where nobody looks. Behind a curtain, above a door, on the wall behind the sofa. On a long run you usually get to choose.
This is also the argument for buying longer stock. A 16 ft stick covers more walls without a joint, but long molding is the stock that arrives with a bow in it, and a bowed stick shows a shadow line against the ceiling that no amount of nailing will pull out. Straight 12 ft material beats a bent 16 ft stick every time.
Does the building code cover crown molding?
No. Crown molding is finish carpentry, and the International Residential Code does not regulate it. There is no code figure for the angles on this page — they are geometry, not law, and they come from the profile of the molding, not from a code book.
The only code that touches a ceiling is R305.1, which sets a minimum ceiling height of 7 ft in habitable rooms. Crown molding does not count against that, because it sits at the ceiling line rather than below it.
What actually constrains this work is three things you measure yourself: the corner angle (rarely exactly 90°), the spring angle of the profile you bought (38° or 45°), and the length of the sticks you can handle. All three are worth checking before you cut anything.
Worked example: a 20 × 16 ft room
Take a rectangular room 20 feet by 16 feet, with 38° crown, four inside corners and no outside corners. You are buying 12 ft sticks and allowing 10% waste.
The run along the ceiling is the perimeter: 2 × (20 + 16) = 72 ft. Add 10% waste and you need 79.2 linear ft. In 12 ft sticks that is 6.6 pieces, so you buy 7 pieces, which is 84 linear ft — about 5 ft more than the job needs, and that surplus is what covers a bad cut.
Four inside corners means 8 miter cuts, two at each corner, one on each piece that meets there. The longest wall is 20 ft, so that run needs two pieces with one scarf joint between them.
The saw settings are the ones in the first table: miter 31.6°, bevel 33.9°. Cut a test pair in scrap first — with only 8 cuts to make, a wrong spring angle is the difference between a job that closes up cleanly and one with four open joints you cannot caulk on a stained profile.
Frequently asked questions
What angle do you cut crown molding at?
For a square 90° corner, 38° crown cuts at a miter of 31.6° and a bevel of 33.9°. The same corner in 45° crown cuts at a miter of 35.3° and a bevel of 30°. Both settings assume the molding is cut flat on its back on the saw table, with the table swung and the blade tilted together. Nest the molding in the saw at the angle it sits on the wall instead and these numbers do not apply — a nested cut is a plain miter, 45° at a square corner whatever the spring angle.
How do I know if my crown molding is 38° or 45°?
Stand the molding in the corner it is going into and see how it sits — flat against the wall and flat against the ceiling, no rocking. If it rocks against one or the other, you have the wrong spring angle. As a starting point, 3⅝ in and 5¼ in profiles are usually 38°, and 3¼ in and most 5½ in and larger profiles are usually 45°, but the profile you actually bought is the only thing that counts. The two settings are 4° apart and the wrong one opens every joint in the room.
Why are the miter and bevel different numbers?
Because the molding is cut at an angle to both the wall and the ceiling at the same time. A flat piece of trim laid against a wall only has to turn in one plane, so its miter alone does the work. Crown leans back at its spring angle, and the corner turns in the horizontal plane, so the cut has to be tilted and swung at once — a compound miter. That is why a miter saw doing crown work uses both scales together, and why the two numbers never match.
Can I cut crown molding nested instead of flat?
You can, and many carpenters do. Nest the molding in the saw at the angle it sits on the wall — ceiling edge flat on the saw table, wall edge against the fence — and the cut becomes a plain miter with no bevel: 45° at a square corner whatever the spring angle. That is its advantage, and it is why the method needs no chart. What it needs instead is a fence tall enough to hold the molding on edge without the blade fouling it, which rules out most small saws on 3¼ in and larger profiles, and a steadier hand, because the molding is standing up rather than lying flat. The angles on this page are the flat cut.
How much crown molding do I need for a 12 × 12 room?
The run is the perimeter, 4 × 12 = 48 ft. Add 10% waste for 52.8 linear ft. In 12 ft sticks that is 4.4 pieces, so you buy 5 sticks, or 60 linear ft. You would make 8 miter cuts at the four corners. If the room has outside corners, a bay window or walls that are not square, go to 15% waste instead — the extra cuts are where material gets eaten.
How much waste should I allow for crown molding?
10% for a plain square room with four corners and no joins. 15% where there are outside corners, bay windows, angled walls or a lot of scarf joints. Go higher again if the molding has a deep profile that is hard to line up, or if you are staining rather than painting — you cannot hide a bad joint with caulk and paint. Waste on crown is not really waste; it is the cost of the test cuts that tell you the spring angle was right.
Do inside and outside corners use the same angles?
Yes. A 90° inside corner and a 90° outside corner both cut at a miter of 31.6° and a bevel of 33.9° in 38° crown. What changes is which side of the blade the cut is on: for an outside corner you swing the miter to the other side of zero and cut the opposite end of the stick. Same numbers, same setup, mirrored.
How do I join crown molding on a wall that is too long for one stick?
Cut a scarf joint on a 45° angle rather than square, so the joint sits inside the profile instead of showing as a straight line across the face. Land it over a ceiling joist or a stud so both pieces can be pulled tight, glue it, and nail both sides. Then place it where it will not be looked at — behind a curtain or above a doorway. If you would rather not make the joint at all, buy longer stock, but check the sticks for bow before you pay for them.