Sixty-five feet at the rack, thirty-two board feet at the shed
The room is nineteen feet by thirteen and a half, the ceiling line round it is sixty-five feet, and two counters in the same yard will price that identically-measured room in two units that never meet. The moulding rack sells sticks: a stock profile off a shelf, in whatever ladder of lengths that supplier runs, quoted by the lineal foot and handed over as whole pieces you then have to make a room out of. The hardwood shed sells volume: rough boards in random widths and random lengths, tallied in board feet, priced by the board foot against a grade, and completely indifferent to the fact that your longest wall is nineteen feet and not eighteen or twenty.
Everything awkward about ordering crown lives in the gap between those two counters. A perimeter is a length and a stick is a length, so the temptation is to divide one by the other and go home — and that division is wrong in a specific, expensive way at the rack. It is not even the right kind of number at the hardwood counter, where a length has to be converted into a volume before anybody will quote it at all. The job below is walking from one measured room to both counters without doing the arithmetic twice and without getting a different room each time.
The ceiling perimeter is not the floor perimeter
Crown runs above every opening in the room, which is the one genuinely easy thing about it: no door widths to deduct, no window reveals to work round, no threshold to negotiate. It is also why the perimeter usually gets taken off the floor plan out of habit — twice length plus width is quicker than getting a ladder out, and in a plain box of a room the two numbers are the same.
They stop being the same the instant anything hangs off the ceiling. A boxed-in soil stack in the corner of a bathroom turns one internal corner into two internals and an external, and adds its girth. A bulkhead over the kitchen units adds both its faces and its return ends, each of which is a crown run in its own right. A dropped beam case takes crown down both sides and, if the client wants it carried round, both ends as well. A chimney breast adds two external corners and twice the depth of the breast. None of that is visible on a floor plan and none of it is in twice length plus width.
Then there is the direction the walls lean. A room that measures square across the floor is very often not square up at the trim line, because plasterboard bows, studs twist and an old lath wall does whatever it has spent a century deciding to do. Measure at the ceiling, wall by wall, and write each run on the plaster where it can be read from the ladder. While you are up there, count the corners and note their hand, because the internal and external counts are what set the allowance and they are also what you will hand the saw.
- Measure every wall at the ceiling line rather than off the floor plan, and write the run on the plaster.
- Add the girth of each bulkhead, beam case, boxed stack and chimney breast as its own run with its own corners.
- List internal and external corners separately — the externals are the ones that cost stick length as well as time.
- Note which way the ceiling joists run against each wall, because that decides where a joint is allowed to fall and where a nailer will be needed.
- Sight the ceiling for its worst dip and mark where it lands, so the decision about following the ceiling or following a level line is made on the floor rather than on the ladder.
Spring angle fixes the drop, the projection and both saw settings
A crown is a sprung moulding: it touches the wall along one back edge, the ceiling along the other, and the triangular void behind it is the entire point of the section. The angle it sits at is the spring angle, quoted as a pair, and two pairs fill most racks — 38/52 and 45/45. Check which of the pair your supplier means, because catalogues disagree about which number leads. The definition worth carrying is the angle between the back of the moulding and the wall: 38 degrees for the common profile, 45 for the square one, with the complement going to the ceiling.
From that single angle and the face width, everything else falls out. Face width times the cosine of the spring angle is the drop down the wall. Face width times the sine of it is the projection onto the ceiling. A 5-1/4 inch crown at 38 degrees therefore drops 4-1/8 inches and projects 3-1/4, and knowing those two numbers before you buy tells you three things you would otherwise discover the hard way: how far down the wall the paint line has to reach, how much length each external corner is going to eat, and whether the moulding will stand up against your saw fence at all.
The external corner deserves its own moment. At an internal corner both back edges die into the corner and the piece is simply the wall dimension. At an external one the ceiling contact line stands off the wall by the projection, so the two contact lines cross at a point one projection beyond the corner along each wall — meaning every external corner adds a projection's worth of stick to each of the two pieces meeting there. On eighteen millimetre skirting that is a rounding error nobody bothers with. On a 6-3/4 inch crown it is 4-3/16 inches per piece, and a chimney breast — two external corners, so four piece ends — has quietly eaten nearly seventeen inches before anyone has made a cut.
Cutting splits into two methods and the drop decides which one is available. Nested — upside down and backwards, the ceiling edge flat on the saw table and the wall edge against the fence — reproduces the room's own geometry on the machine, so a square corner becomes a plain 45 degree mitre with the bevel scale left at zero and one setting to get wrong instead of two. That only holds while the fence is taller than the drop. Once the moulding is too big to stand up, it goes flat on the table and both scales come into play together.
Those two settings are trigonometry, not a lookup. The mitre is the arctangent of the sine of the spring angle divided by the tangent of half the corner angle; the bevel is the arcsine of the cosine of the spring angle multiplied by the cosine of half the corner angle. Feed in a square corner and a 38 degree spring and they return 31.6 and 33.9, which are the numbers printed in every compound saw manual; a 45 degree spring returns 35.3 and 30.0. The reason to carry the relations rather than the chart is that no corner in an occupied house is square. A corner measuring 88 degrees wants 32.5 and 34.5. One measuring 92 wants 30.7 and 33.2. The 135 degree corner of an octagonal bay wants 14.3 and 17.6, and it is not in any chart at all. An external square corner takes the same 31.6 and 33.9 as the internal one — what reverses is which side of the blade the keeper is on and which end of the stick it comes off.
| Face width | Drop down the wall | Projection onto the ceiling | Nested or flat | Rough blank |
|---|---|---|---|---|
| 3-1/2 in (89 mm) | 2-3/4 in (70 mm) | 2-3/16 in (55 mm) | Nested against any fence | 4 in |
| 4-5/8 in (117 mm) | 3-5/8 in (93 mm) | 2-7/8 in (72 mm) | Nested on most saws | 6 in |
| 5-1/4 in (133 mm) | 4-1/8 in (105 mm) | 3-1/4 in (82 mm) | Marginal — measure your own fence | 6 in |
| 6-3/4 in (171 mm) | 5-5/16 in (135 mm) | 4-3/16 in (106 mm) | Flat, on compound settings | 8 in |
| 8 in (203 mm) | 6-5/16 in (160 mm) | 4-15/16 in (125 mm) | Flat, and check the saw's cut capacity too | 9 in |
Give it the spring angle measured off the stock and the corner measured at ceiling height, and it returns the pair of settings for cutting flat and the single setting for cutting nested, for any corner the house actually has rather than the square one the chart assumes.
A corner of flat trim, a closed frame of equal sides, or a sprung crown moulding.
The corner measured across the room's side: under 180 for an internal corner, over 180 for an external one.
Mitre setting on the saw
45 °
An internal corner, read through the room at under 180°. The scale reads the swing from a square cut, so the setting is 90° less half the corner, and both pieces are cut at it in opposite hands. In skirting or baseboard an internal corner is often coped instead, the second board scribed over the first, because a coped joint stays closed when the wall is off square; a mitre is the usual joint wherever the ends of both pieces would otherwise show, as round a window or on a frame.
- Angle between each cut and the edge of its piece
- 45 °
- Angle the two pieces include
- 90 °
- Turn of the trim at the corner
- 90 °
They open the calculator with your figures already in it
Miter Angle Calculator — Mitre Saw Corners, Frames and Crown: 45 ° — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
What this calculation does not cover
- The settings are magnitudes. Which way the table swings, which way the blade tilts, which edge of a crown goes against the fence and which side of the cut is kept depend on whether the piece is the left or the right one and whether the corner is internal or external, and they differ between saws; follow the maker's chart for the saw in use and cut a trial pair from offcuts first.
- The corner has to be measured, not assumed. A plastered corner a degree or two off square is ordinary, and the error goes straight into the joint, so read each corner with an angle finder or a sliding bevel at the height the trim will run.
- Both pieces are taken as the same width and section. Two trims of different widths meeting at a corner need a different cut angle on each, and a frame of unequal sides needs each joint worked separately.
- A setting near or past the end of a saw's scale needs a jig or a hand cut. The DeWALT DWS779 cited here mitres to 60° one way and 50° the other and bevels to 49°, so very sharp corners and small polygons can run off the scale; check the saw before buying stock for an unusual shape.
- The crown settings depend on the spring angle entered. A moulding whose real spring differs from the figure used will gap at the ceiling or the wall however carefully the settings are dialled in, and the nested method only works while the moulding's drop fits under the fence.
- Only angles are given: the length of each piece, the stock to buy and the offcuts lost to mitres are left to the trim and crown take-off pages.
Whole sticks, and the offcut that has a hand
This is where a perimeter stops being a length. Crown is racked in a ladder stepping two feet at a time from 8 to 16 feet where mouldings are milled to imperial sizes, and running 2.4, 3.0, 3.6, 4.2 and 4.8 metres where they are milled to metric ones — and those are two different products rather than one product seen through two unit systems. Whichever ladder your merchant runs, the arithmetic that decides the order is per wall. A wall is covered by whole sticks, or by a stick plus a joint, and a total-footage figure divided by a stock length knows nothing about which of those it just bought.
Take a thirteen foot square room. Perimeter fifty-two feet; add the usual fifteen per cent for compound cuts and it is 59.8; divide by a twelve foot stick and the answer is five. Five twelve-foot sticks is sixty feet of crown and four joints, one on every wall, because thirteen is twelve plus one and nobody scarfs a one-foot tail onto the end of a run. Four fourteen-foot sticks is fifty-six feet, no joint anywhere in the room, and one fewer piece to carry up the stairs. The waste allowance was not wrong — it was answering a different question. It says how much material the cutting will consume. It does not say which length to buy, and the length is the decision.
Two things then constrain what can be done with what is left over, and neither applies to flat trim. The first is hand. Every end of a fitted crown piece carries a cut belonging to one particular corner: a left-hand internal, a right-hand external, the bevelled half of a scarf. An offcut with a live end is only reusable where that end fits, which on a four-corner room is about half the corners — and on a nested cut it has to have come off the correct end of the stick in the first place. The second is where a joint is permitted to be. A crown scarf is a bevelled lap, glued and nailed through both halves, and it needs solid backing behind it, which means it lands on a joist or on a nailer rather than wherever the tape says the stick ran out. Plan the joint onto the framing, put it on the wall furthest from the door, and keep it away from the middle of the longest run, which is exactly where the eye settles.
The piece-count argument for a closed perimeter in general — that a room breaks into as many runs as it has corners, and no run can be made from less than one piece — is worked through for perimeter trim in the large ceiling guide and holds here without restatement. What is added on a sprung moulding is that the pieces are not interchangeable once they have been cut.
| How the order was arrived at | Sticks | Crown bought | Joints in the room | What that buys |
|---|---|---|---|---|
| Perimeter plus 15 per cent, divided by a 12 ft stick | 5 x 12 ft | 60 ft | 4 — one per wall | Four bevelled scarfs, each landing twelve feet from a corner whether or not a joist is there |
| One stick per wall, chosen against the run | 4 x 14 ft | 56 ft | 0 | Four feet less timber, nothing to glue, nothing to sand, one fewer piece on the van |
| One stick per wall at the next length up | 4 x 16 ft | 64 ft | 0 | Also jointless, at twelve feet of offcut — eight feet more than the fourteens — and a stick that will not turn on a domestic landing |
It takes twice length plus width at the ceiling, adds fifteen per cent for the compound cuts and divides by the stick you select — a material allowance and a floor on the order rather than a cutting plan. Two corrections before it becomes an order: redo the count wall by wall against the ladder your merchant actually racks, since going up one length often buys less timber and no joints, and enter every bulkhead, beam case and chimney breast as its own run because a rectangle does not know they exist.
SettingsSettings for this calculation
Waste is set to 15% by hand. Pick a tier above to replace it, or keep your own figure.
The longer wall, measured at ceiling level.
The shorter wall, measured at ceiling level.
The length crown molding is sold in at your supplier.
Extra run for compound-mitre corners, test cuts and the piece that comes up short.
The angle the back of the molding makes with the wall when it is in place.
The angle the two walls include at the corner, measured in plan.
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.
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.
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.
What the crown is actually nailed to
A crown fixed along both back edges is fixed to two different things, and one of them is frequently not there. The wall edge finds the top plate behind the board, which is continuous, reliable and exactly where you expect it. The ceiling edge is looking for a joist — and finds one only on the walls the joists run into. On the two walls they run parallel to, there is nothing above the board within reach of a nail except whichever joist happens to sit near that wall, and on a ceiling hung on furrings or resilient bar, not even that.
The answer is a nailer: a continuous strip set in the void behind the moulding, screwed to the plate and to whatever framing is genuinely there, with its face landing where the crown's back wants to sit. Rip it on the diagonal from dimensional stock and it fills the triangle; leave it square in section and it offers one bearing face, which is sufficient provided the face is set to the right offset — and that offset is the drop and projection from the table above, not a guess. Either way it converts a fixing problem into a setting-out problem, which is a good trade, because the moulding's position is now decided by where the nailer went rather than by how hard somebody pressed it into the corner.
That change is worth more than the fixing. A crown held to two surfaces follows both of them, so a ceiling that dips carries the moulding down with it and a wall that bellies pushes it out into the room; a crown held to a nailer follows the nailer. Over a long wall in an old house that is the difference between a line and a wave. The nailer also gives every scarf somewhere solid to land, and it lets you set the moulding deliberately clear of a bad ceiling and caulk the gap as a decision rather than as an apology.
What is behind a run of crown
- Crown moulding — the only layer anyone sees, bought as whole sticks against the ceiling perimeter and the corner count rather than by the metre Crown Molding Calculator
- Nailer in the sprung void — a continuous rip filling the triangle behind the moulding, the fixing on every wall the joists run parallel to Lumber Dimensional Size Calculator
- Ceiling and wall board — the two finished faces the crown's back edges bear on, and the reason a nail has thirteen millimetres to cross before it reaches anything solid Ceiling Plasterboard (Gypsum Board) Sheet Calculator
- Top plate and joist ends — the structure the whole assembly is hung on, and whose direction decides which walls need a nailer at all Ceiling Joist Spanning Lineal Lumber Aggregator
Priced by the board foot, cut by the lineal foot
Nothing on the rack matches the profile in a Victorian front room, and at that point the job stops being a shopping trip and becomes an order for rough stock plus machining. The unit changes with it. The moulding was lineal feet; the timber is board feet, which is a volume. The definition itself, the quarters convention for thickness and the grade's clear-cutting yields that decide how much of a pack is usable are set out in the skirting and architrave guide and are not repeated here. What matters standing at this counter is the conversion running the other way — how a length of moulding becomes a volume of board.
One lineal foot of moulding consumes one lineal foot of the blank it is machined from, so board feet per lineal foot is nothing more than the blank's nominal thickness in inches times its width in inches, over twelve. A six inch blank in 4/4 is exactly half a board foot for every foot of moulding, so the sixty-five foot room at the top of this page, in a 5-1/4 crown machined from that blank, is thirty-two and a half board feet net before a single allowance. That one factor is also what lets a millwork quote priced per lineal foot be compared with rough stock priced per board foot without guessing: multiply the yard's board-foot figure by the factor and you have their timber cost per foot of finished moulding, and whatever separates that from the millwork quote is what the setup, the machining, the sanding and the mill's risk are worth. This site publishes no prices and does not need to — the comparison works on whatever two numbers the two suppliers give you on the day.
The blank is always wider than the crown. A sprung moulding is machined out of a flat board with the two back bevels cut off its edges, so the board has to carry the face width plus enough to joint both edges and hold the piece down through the cutter — call it half an inch, rounded up to the whole inch the mill tallies in. That rounding does something useful and something annoying. Useful first: a 4-5/8 crown and a 5-1/4 crown both come out of a six inch board, so the wider profile is free in board feet and costs only in machining. Annoying second: what you are handed is a random-width pack, and a board tallied at six inches under a surface-measure rule can physically be five and a half. Sorting the pack for usable width is part of the buy rather than a grievance about it.
Length is the other half of the same problem, and it is the half that gets underestimated. Hardwood arrives in random lengths, mostly even feet from six to sixteen, and the mill's length distribution governs your yield more directly than the grade does. Your cutting list is a set of lengths no mill has ever heard of: a thirteen foot wall wants a fourteen foot board and there is no such thing as ordering fourteens. So take the net board feet, add for the rips and the jointer passes — a saw kerf plus two clean edges is easily three eighths of an inch gone off every rip — add again for the grade's clear-cutting yield, and again for the lengths that will not yield a piece on your list. The order leaving the shed sits comfortably a third above net, and that is not padding. It is the arithmetic difference between a volume of timber and a list of pieces.
Run it on the blank, never on the finished moulding: nominal thickness in quarters, the blank width you settled on after the jointing allowance, the length in feet, and a board count that is the number of blanks rather than anything to do with the room. Treat the answer as net — rips, yield and the lengths the mill actually holds all sit between it and the order.
The board's NOMINAL thickness — a board sold as one inch measures about 3/4 in once surfaced, and board footage is charged on the nominal size.
The board's width.
The board's length.
How many identical boards you're calculating for.
Total board feet
4 board feet
- Per board
- 4 board ft
- Number of boards
- 1 board
- Cubic feet (total)
- 0.33 cu ft
They open the calculator with your figures already in it
Board Feet Calculator: 4 board feet — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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.
What this calculation does not cover
- Nothing in the calculation maps nominal sizes onto actual milled ones — thickness, width and length are multiplied exactly as typed, so entering the surfaced 1.5 x 3.5 in (89 mm) of a 2x4 returns that board's true volume instead of the nominal footage it is invoiced at.
- No waste, kerf or cutting-defect allowance is folded in: the figure is the finished footage sitting inside the boards, so rough or random-width stock needs its own margin added on top of it.
- Length is used exactly as entered and is never rounded up to a stock length, so a 7.5 ft requirement stays 7.5 ft rather than becoming the 8 ft board the mill actually sells.
- Per-board footage is carried through as an unrounded decimal and multiplied by the board count, with no rounding applied piece by piece, so the total will drift from a tally that rounds each board before adding it.
- The board-count field repeats one identical board, so a cutting list of mixed thicknesses, widths or lengths has to be run size by size and the answers added together by hand.
- The cubic-feet line is a straight division of the board-foot total by twelve — the solid volume of the wood itself, not the stacked space a delivery occupies once stickers and uneven lengths are accounted for.
Built up from three small mouldings
There is a way around most of the above and it is not a compromise. A large crown can be assembled on the wall out of small ones: a bed or a cove sprung in the corner, a flat frieze board on the wall, a cap running along the ceiling. The assembly reads bigger than anything on the rack and every component fits under a saw fence, so the whole compound-flat-cut problem never arises.
The order changes shape completely. Instead of one wide blank you are buying three narrow ones, and narrow is exactly where a random-width hardwood pack is generous — the four and five inch boards that were useless for a single wide crown are what the components want. The board-foot figure usually falls for the same visual size, because a built-up profile is mostly air. Against that: three runs of moulding, three sets of corners to cut, joints that have to be staggered so no two land on the same joist, and a total drop and projection that has to be worked out from the three components rather than read off a catalogue page.
Two practical gains repay the extra corners. The frieze board gives the whole assembly a continuous, dead flat fixing surface, which disposes of the ceiling-edge nailing problem before it comes up. And a built-up crown is adjustable on site in a way a single stick is not: where a ceiling is forty millimetres out over the length of a wall, the frieze absorbs the discrepancy and the cap covers it, whereas one sprung length has nowhere to put it and shows the whole error as a tapering shadow.
Setting the line before the first stick is cut
Every decision above lands on one line marked on the wall. Shoot the drop at each corner from a laser levelled to the room, rather than measuring down from the ceiling with a tape, which only reproduces the ceiling's own faults. Then read the spread across the room. If the worst of it is a millimetre or two, work off the ceiling and let the bottom edge follow. If the ceiling is genuinely out, hold the crown to the level line, accept the wedge of a gap at the top and caulk it: the eye reads the bottom edge of a crown as a horizontal and reads the top edge as a shadow it has no way of measuring.
The one thing not to do is split the difference silently. A moulding made to follow the ceiling at one end and the level line at the other twists along its length, opens the back of every joint it runs into, and comes off the wall within a season. Choose which surface is telling the truth, write the drop on the plaster at every corner before the saw is set up, and cut to that figure rather than to whatever the tape says on the ladder.
Pricing a room's crown
Two counters, two units, one room. The stick count comes off the walls and the board-foot figure comes off the blank, and the order that leaves the yard has to satisfy both without either being converted into the other.
- Ceiling perimeter, wall by wall — Measured at the trim line rather than off the floor plan, with the girth of every bulkhead, beam case, boxed stack and chimney breast added as a run of its own.
- Corners, counted by hand — Internals and externals listed separately, since each external adds one projection's worth of stick to both pieces meeting at it — inches on a large crown, not millimetres.
- Stock length, chosen rather than divided — The ladder your merchant actually racks, tested against each wall run; moving up one length frequently buys less timber and removes every joint in the room.
- Nailer for the parallel walls — A continuous rip behind the moulding wherever the joists run the wrong way, priced as timber and screws rather than assumed into a trim rate.
- Blank section, not finished section — Nominal thickness in quarters and the face width plus a jointing allowance, rounded up to the inch the mill tallies in — that is the section board feet are charged on.
- The gap between net and order — Rips, jointer passes, the grade's clear-cutting yield and the lengths the mill actually holds, taken as four separate allowances rather than one blanket percentage.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.