SettingsSettings for this calculationUS
Waste is set to 15% by hand. Pick a tier above to replace it, or keep your own figure.
A four-walled room by its sides, or the whole line where walls meet ceiling in any other room.
Crown follows the top of every wall, so an L-shaped room, a bay or a bulkhead is taken at ceiling height, return by return, and the lengths added into one run; each extra corner is a mitre, so consider a higher allowance below for a room with many.
The longer wall, measured at ceiling level.
Take it at the ceiling rather than at the floor wherever the two differ, because crown follows the ceiling line and the two perimeters are not the same room. A bulkhead over kitchen units, a dropped soffit, a boxed-in beam and a chimney breast all add a return the floor plan does not show — and each return adds two more corners, which on crown is the expensive part rather than the extra length.
Tools needed: Tape measure
The shorter wall, measured at ceiling level.
Measure at both ends and use the larger of the two. Rooms are rarely square, and crown is unforgiving about it in a way skirting is not: the profile has to meet its neighbour exactly along a mitre that is already compound, so a piece cut to the short reading leaves a gap that no amount of caulk hides under raking light.
Tools needed: Tape measure
The length crown molding is sold in at your supplier.
The trade-off is sharper overhead than it is at floor level. A long stick means fewer scarf joints, and a scarf in crown is far more visible than one in skirting — it sits at eye line under lighting that rakes along it, and it opens as the timber moves. Against that, a 16 ft length has to be carried up a ladder and held at its spring angle by one person while the other cuts, which is where long stock gets snapped. Most fitters take the longest stick the room and the stairs will actually admit, and no longer.
Extra run for compound-mitre corners, test cuts and the piece that comes up short.
Fifteen per cent is the usual figure for crown, above flat trim's ten, because every corner is cut at a compound angle. A room with outside corners, or a first crown job, justifies more; a long plain run with two inside corners, less.
The angle the back of the molding makes with the wall when it is in place.
Two profiles account for almost everything sold: 38/52 and 45/45, named for the two angles the back of the stick makes with the wall and the ceiling. Enter the WALL figure — 38 for the first, 45 for the second — and if you are unsure which you have, hold a stick in place against a square and read the angle off the wall leg rather than trusting the invoice. It is the single largest influence on both cut angles below: the same square corner takes 31.62° on the table with a 38° crown and 35.26° with a 45° one, so cutting a 45/45 stick to the 38/52 settings leaves a gap at the ceiling that filler cannot hide.
The angle the two walls include at the corner, measured in plan.
The angle BETWEEN the walls, not the angle the molding turns through: 90 for a square corner, 135 for the obtuse corner of a bay, 45 for the sharp one. The two readings are the same number at a square corner and nowhere else, which is exactly how compound-mitre settings are got wrong — a 135° bay wants 14.3° on the table, and the 56° that comes of entering the turn instead is not a cut anyone can use. Measure the corner rather than assuming it: a plastered internal corner is routinely a degree or two off square, and crown magnifies that because the cut is compound.
Crown molding needed
56.35 linear ft
- Ceiling perimeter
- 49 linear ft
- Sticks needed
- 8 x 8 ft sticks
- Mitre, set on the saw's table
- 31.62 °
- Bevel, set on the saw's blade
- 33.86 °
They open the calculator with your figures already in it
Crown Molding Calculator: 56.35 linear ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- Room perimeter = 2 x (length + width); crown molding runs the full ceiling perimeter since doorways don't reach the ceiling
- 15% waste is standard for crown molding to account for compound-angle corner miters, higher than flat trim's typical 10%
- Crown molding is racked in 8, 10, 12, 14 and 16 ft sticks where trim is sold by the foot, and in 2.4, 3, 3.6, 4.2 and 4.8 m sticks where it is sold by the metre, that ladder climbing in 300 mm steps
- Compound mitre for a sprung moulding cut flat on the saw: miter = arctan(sin S · tan(A/2)) and bevel = arcsin(cos S · sin(A/2)), where S is the spring angle and A is the angle the moulding TURNS — 180° less the angle the walls include. Reproduces the settings every crown table prints: 31.62°/33.86° for a 38/52 crown at a square corner, and 35.26°/30° for a 45/45
Inputs used
- Ceiling Measured As
- A rectangle (length and width)
- Measured Ceiling Run
- 49 ft
- Room Length
- 13 ft
- Room Width
- 11.5 ft
- Stock Stick Length
- 8 ft
- Mitre Waste (%)
- 15
- Spring Angle of the Molding
- 38
- Angle Between the Walls at the Corner
- 90
Intermediate steps
- Ceiling perimeter
- 49 linear ft
- Sticks needed
- 8 x 8 ft sticks
- Mitre, set on the saw's table
- 31.62 °
- Bevel, set on the saw's blade
- 33.86 °
What this calculation does not cover
- Only a length and a width are collected, so the ceiling line is taken as a plain rectangle at 2 x (length + width) — an alcove, a bay, an L-shaped plan or a ceiling that steps around a stairwell opening is longer than that formula returns. Total such a ceiling as two or more rectangles, run each one separately, and add the stick counts.
- The mitre waste is a single percentage on the whole perimeter rather than a per-corner allowance, and neither the corner count nor the profile size is asked for, so a square room with four inside corners and an L-shaped one with six are padded alike unless the percentage is raised for the second.
- Sticks needed is the padded run divided by one stock length and rounded up, which pools every offcut as though the molding were continuous: in the room each wall is cut to its own length, a wall longer than one stick has to be made up from two pieces joined mid-run, and an offcut already cut at a compound angle on one end suits only a corner of that hand. One stock length also applies to the whole room, so an order that mixes 16 ft pieces on the long walls with 8 ft on the short ones cannot be costed here.
- Metric and imperial stock are two different products in this table rather than one length read twice, so changing the page's measurement system re-reads the same selection as 2.4 m where it had been 8 ft. The metric side can come out a stick higher for a room that has not changed, and the two counts are not comparable against each other on price.
- The two cut angles are for the molding laid FLAT on the saw table, which is the method that needs both settings. Cutting it nested — held against the fence at its spring angle, the way it sits on the wall — is a different method with its own fixed settings and these numbers do not apply to it. Decide which method you are using before you cut, because both produce a plausible-looking joint from the wrong one.
- An inside corner and an outside corner of the same angle take the SAME two settings; what changes is which side of the line is waste and which way the stick is handed. The page cannot tell you which, because it never asks whether the corner turns into the room or out of it, and getting that wrong wastes a stick rather than producing a bad joint.
- Molding length is the whole of what comes back — backing blocks, adhesive, brads and filler all sit outside the figure — and each room dimension stops at 30 m, so a hall or an open-plan ceiling longer than that has to be split into runs and its stick counts added.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Part of a bigger job
Or plan the space itself: measure it once, doors and windows included, and this figure comes back worked out on that space, with what goes with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-17 · v1.1.0
Regulatory standards & verification citations4
- Room perimeter = 2 x (length + width); crown molding runs the full ceiling perimeter since doorways don't reach the ceiling
- 15% waste is standard for crown molding to account for compound-angle corner miters, higher than flat trim's typical 10%
- Crown molding is racked in 8, 10, 12, 14 and 16 ft sticks where trim is sold by the foot, and in 2.4, 3, 3.6, 4.2 and 4.8 m sticks where it is sold by the metre, that ladder climbing in 300 mm steps
- Compound mitre for a sprung moulding cut flat on the saw: miter = arctan(sin S · tan(A/2)) and bevel = arcsin(cos S · sin(A/2)), where S is the spring angle and A is the angle the moulding TURNS — 180° less the angle the walls include. Reproduces the settings every crown table prints: 31.62°/33.86° for a 38/52 crown at a square corner, and 35.26°/30° for a 45/45
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.
Tools and safety for this job
To fix skirting and trim. Generic types, no brands, no prices.
Protection this work requires
- Hardwood dust is a recognised carcinogen: extract at the tool and wear a P2/N95 respirator when cutting or sanding indoors.
- Saws, grinders and breakers run above 85 dB, where hearing damage accumulates and does not recover: defenders or plugs for every cut, not just the long ones.
- Nailing, chiselling and cutting all throw fragments: glasses to EN 166 or ANSI Z87.1, and goggles rather than glasses overhead.
Show the 6 tools this job needsHide tools
Essential
Claw hammer
Combination or framing square
Mitre saw
Recommended
Brad or finish nailer
Caulking gun
Filling knife
Also needed as materials: brad nails, caulk and sealant cartridges, mitre saw blades.
what each carpentry tool is for, and the spec that decides which to buy where one does.