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Crown Molding Calculator

Get the miter and bevel saw settings for cutting crown molding flat on a compound miter saw, for any spring angle and any corner.

Level: Grades 10–11

Printable worksheet

Crown Molding Calculator

Know the answer you need? Pick an input to work backward.

Inputs

Most crown is 52/38 (enter 38) or 45/45 (enter 45). Check the profile or measure it against a square.

90 for a square corner, 135 for a typical bay. Inside and outside corners use the same angles.

Result

Miter setting (molding flat on the saw)

31.62 °

For 38° crown on a 90° corner, cut flat at a 31.62° miter and 33.86° bevel, or nested at 45° with no bevel.

Bevel setting (molding flat on the saw)
33.86 °
Miter setting (nested, no bevel)
45 °
Angle between molding back and ceiling
52 °

See the step-by-step solution ↓

Step-by-step solution

  1. Half the wall angle: each piece covers half the corner

    902=45 °

  2. Find the miter for a flat cut. This trig formula combines the spring angle with half the corner

    arctansin38 °×cos45 °sin45 °=arctan0.615661×0.7071070.707107=31.619 °

  3. Find the bevel (blade tilt) for a flat cut, again from the spring angle and half the corner

    arcsincos38 °×cos45 °=arcsin0.788011×0.707107=33.8629 °

  4. For a nested cut (upside down against the fence), the molding is already tilted. So the miter is just 90° minus half the corner, with no bevel

    90−45=45 °

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

What this calculator does

Get the exact saw settings for cutting crown molding to fit any corner. Crown molding sits on a slant between the wall and the ceiling. So where two pieces meet in a corner, the joint is angled in two directions at once. Cutting it with the molding lying flat on a compound miter saw takes two settings. The miter is how far the saw swings across the board. The bevel is how far the blade tilts. Both depend on how steeply the molding sits, called its spring angle, and on the angle between the walls.

This calculator gives both settings for any spring angle and any wall angle. So bay windows, angled walls and rooms that aren't quite square are as easy as square corners. It also gives the simpler nested setting. That's used when you hold the molding upside down against the saw's fence at its installed angle. Walls are rarely perfectly square. So measure the real corner, test the cut on scrap pieces and adjust before cutting long lengths.

Where it's used

Why this math matters outside the classroom:

  • Square room corners. Trim carpenters cut 52/38 crown flat at a 31.62° miter and 33.86° bevel for every square inside corner.
  • Bay window ceilings. Installers fitting crown around a 135° bay corner use a 14.31° miter and 17.55° bevel for 38° crown cut flat.
  • Cabinet tops. Cabinet makers run small crown along cabinet tops, where outside corners take the same angles mirrored.
  • Saw detents. Saw makers put detents near 31.6° and 33.9° on miter saws so the common 52/38 square-corner cut sets quickly.
  • Trig practice. Students apply arctangent and arcsine to a real compound angle by checking that 45° crown gives a 30° bevel on a square corner.

Grade level and standards: Grades 10–11; Common Core State Standards for Mathematics HSG.SRT.C.8. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Find the spring angle. Use 38 for the common 52/38 profile or 45 for 45/45 crown, or measure it.
  2. Measure the angle between the walls with an angle finder or bevel gauge. Or use 90 for a square corner.
  3. Read the flat-cut miter and bevel. Or read the nested miter, if you cut the molding upside down against the fence.
  4. Cut both pieces of a test joint from scrap and hold them up in the corner. Adjust by a fraction of a degree if needed.

What the inputs mean

Spring angle (back of molding to the wall)
The angle between the back of the molding and the wall. Rest the molding against a framing square, and it's the angle its back makes with the upright leg. A 52/38 crown sits 38° from the wall and 52° from the ceiling.
Angle between the walls
The angle the two walls make with each other at the corner. For an inside corner, measure inside it. For an outside corner, measure around it. A square room is 90°, and a typical bay window corner is 135°.

Formula and method

h = wall angle ÷ 2
flat-cut miter = arctan(sin spring ÷ tan h)
flat-cut bevel = arcsin(cos spring × cos h)
nested miter = 90° − h   (no bevel)

Here h is half the wall angle, and "spring" is the spring angle. Sin, cos and tan are the standard trig functions that turn an angle into a ratio. Arctan and arcsin work backward, turning a ratio into an angle. These are the standard formulas for cutting crown molding flat. Laid flat on the saw, the molding's face leans away from the cut by its spring angle. That makes the joint a compound miter, angled two ways at once. The miter is read on the saw's scale from a straight cut. The bevel is read from an upright blade.

Now say you hold the molding upside down against the fence and table at its spring angle. It's already sitting at its installed slant, so only the corner angle is left to cut. That setting is half the corner, taken away from 90°. That's why a square corner is a plain 45° miter when nested, whatever the spring angle.

Worked example

You're installing 52/38 crown (spring angle 38°) in a square room, and you want to cut it flat on the saw.

  1. Half the wall angle: 90° ÷ 2 = 45°.
  2. Miter: arctan(sin 38° × cos 45° ÷ sin 45°) = arctan(0.615661) = 31.62°.
  3. Bevel: arcsin(cos 38° × cos 45°) = arcsin(0.788011 × 0.707107) = arcsin(0.557208) = 33.86°.
  4. Nested alternative: 90° − 45° = 45° miter with no bevel.

Result: Set the saw to a 31.62° miter and a 33.86° bevel for the flat cut. Or use 45° with no bevel if you cut nested.

Understanding the result

Many compound miter saws have preset stops (detents) near 31.6° and 33.9° for 52/38 crown, and near 35.3° and 30° for 45/45 crown. These match the results here for square corners. Other corners need the settings dialed in by hand.

Inside and outside corners use the same numbers. What changes is which end of the piece you cut and which way the saw swings. It also changes whether the ceiling edge or the wall edge rests against the fence. Mark each piece before cutting.

Assumptions and limitations

  • The molding sits at the same spring angle on both walls, tight to the wall and ceiling.
  • The ceiling is level and the walls are plumb (perfectly upright).
  • The saw's miter scale reads 0° for a straight cut, and its bevel scale reads 0° for an upright blade.
  • Real walls and ceilings are seldom perfectly straight. Drywall corners are often rounded or built up. So expect to fine-tune by a fraction of a degree.
  • It doesn't cover coped inside joints, which many trim carpenters prefer. Those are shaped by hand after a starting cut.
  • Saws differ in which way they swing and tilt, so check the direction with a test piece.

Frequently asked questions

What angles do I cut for 38° crown on a 90° corner?

If you cut flat on the saw, use a 31.62° miter and a 33.86° bevel. For 45° crown on a square corner, use 35.26° and 30°. If you cut nested instead, use a plain 45° miter for both.

How do I find the spring angle of my molding?

Set the molding in the corner of a framing square, with its back against both legs, the way it would sit between wall and ceiling. The angle between its back and the upright leg is the spring angle. Many profiles are 38° or 45°. Measuring is still worth it, because some differ.

What is the difference between cutting flat and cutting nested?

Flat cutting lays the molding face up on the table, and it needs both a miter and a bevel. Nested cutting stands the molding upside down against the fence at its installed angle. It needs only a miter. But the molding must be held at exactly the right slant, often with a stop block or jig.

My walls are not square. What should I enter?

Measure the real corner with an angle finder and enter it. If a corner measures 92°, enter 92 rather than 90, and the calculator adjusts both settings. Splitting the measured angle evenly between the two pieces keeps the joint even on both sides.

Sources

How this calculator is checked

Method: Standard compound-angle formulas for crown molding cut flat: miter = arctan(sin S / tan(W/2)), bevel = arcsin(cos S · cos(W/2)); nested miter = 90 − W/2. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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