Two ways to cut crown
Crown molding sits at an angle between the wall and ceiling. That angled position is defined by the spring angle — typically 38° or 45° for stock profiles. How you hold the molding on the saw determines which numbers you dial in: flat on the table with compound miter and bevel, or nested against the fence at the spring angle with a simple miter.
Nested (upside-down on the fence)
The traditional method: tip the crown upside-down against the fence so the ceiling flat contacts the fence and the wall flat rests on the table. The saw stays at 0° bevel; you only swing the miter. For a standard 90° inside corner with 38° spring crown, the miter is 31.6°.
Nested cutting is intuitive — the molding is oriented the way it will sit on the wall, just flipped. The downside is that large crown profiles require a tall fence or a jig, and compound-angle corners (non-90° walls) are harder to visualize.
Flat (compound angles)
Lay the crown flat on the saw table and set both a miter angle and a bevel angle. For the same 38°/90° scenario: miter 33.86°, bevel 29.54°. The flat method handles any wall angle — just change the inputs. It also works better for wide crown on a standard 10″ miter saw because the molding lies flat and does not need fence height.
The trade-off is precision. Two angles instead of one means two chances for error, and small rounding differences in bevel or miter compound into visible gaps on long runs. Always test-fit a scrap piece before committing to finish stock.
Spring angle matters
The spring angle is the tilt from the wall face to the back of the crown. Stock profiles are usually stamped 38° or 45°, but specialty and custom profiles can be anything. Measure it with a combination square if the packaging does not say. Using the wrong spring angle will produce angles that look close but leave a hairline gap on one plane.
Inside vs outside corners
Inside corners (concave) and outside corners (convex) are mirror images of each other in terms of miter direction. Both use the same angle magnitude, but the saw swings to opposite sides. The Crown Calculator shows the miter and bevel for both — enter the wall angle and spring angle and read the inside and outside settings directly.
Non-90-degree walls
Cathedral ceilings, bay windows, and out-of-square rooms change the wall angle from 90° to something else. A digital angle finder on the corner gives you the actual wall angle; plug that into the calculator to get the exact compound or nested cut. Do not assume 90° — most houses are off by 1–3°, which is enough to open a visible gap on large crown.
Coping as an alternative
Many finish carpenters cope inside corners instead of mitering them. Cope one piece to the profile of the other and butt it tight. Coped joints stay tight as the house settles; mitered inside corners tend to open over time. Outside corners still get mitered — there is no practical way to cope an outside joint. The calculator gives you both inside and outside angles regardless of your joinery choice.