Crown Molding Angle Calculator
Spring angle plus your actual corner angle — out come the miter and bevel for cutting flat on the saw, with left/right guidance that ends the guesswork.
Verified against independent hand calculation · sources cited below
31.62°
Miter (table swing)
33.86°
Bevel (blade tilt)
Cutting flat on the saw, finished face up. Inside corner: left piece — miter right, keep the left side; right piece — miter left, keep the right side. Bevel always tilts the same direction; only the miter swings.
Spring angle = the angle the crown leans off the wall (printed on the packaging; 38° is the US standard, 45° common, 52° the flip of 38°). Real corners are rarely exactly 90° — measure with an angle finder and always cut test scraps first.
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, and the famous 31.6°/33.9° detents on your saw are just the 38°-spring, square-corner special case.
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: miter one side square, cope the mate. Copes forgive out-of-square corners that miters telegraph.
Frequently asked questions
What is the spring angle and where do I find it?
The angle the crown leans away from the wall when installed — 38° is the US standard, 45° is common, and 52° is the complement of 38 (same profile hung the other way). It’s printed on the packaging, or measure: set the crown in a framing square as it would sit on the wall and read the lean.
Why are the magic numbers 31.6° and 33.9°?
That’s the miter/bevel pair for the most common case — 38° spring crown in a square 90° corner: miter 31.62°, bevel 33.86°. Most modern miter saws have detents at exactly these settings. This calculator exists for every corner that isn’t 90° — which, in a real house, is most of them.
Flat cutting vs “nested” — which should I use?
Nesting (crown upside-down and angled against the fence, cutting with miter only) works for narrow crown and avoids bevel math. But wide crown won’t fit nested under most saws — cutting flat with a compound angle handles any width, which is what this calculator computes. Pick one method per job and stay consistent.
My corners aren’t 90°. How do I measure them?
Use a digital angle finder or bisect with scrap: real drywall corners commonly run 88–92°, and a 2° error is visible in crown. Measure each corner, punch it into the corner-angle field, and cut test pieces from scrap before touching the good stock — trim carpenters do exactly this.
Sources & further reading
- Standard compound-miter identities: miter = atan(sin S ÷ tan(C/2)), bevel = asin(cos S × cos(C/2))
- Verified against the published reference pairs: 38°/90° → 31.62°/33.86°; 45°/90° → 35.26°/30.00°