Mitre & Bevel Angle Calculator

Printable tables

Every angle, worked out

Mitre saw settings, where 0 is a square crosscut. Both pieces of a corner take the same setting, cut in opposite directions.

Flat trim: skirting, architrave, deck framing

Frames and boxes with equal sides

Cornice cut flat on the saw table

Cut nested instead (held in the saw at the angle it hangs) and there is no bevel at all: the mitre is the flat-trim figure from the first table, which is 45° at a square corner.

Checked against the published tables

Mitre / bevel. Small differences are rounding in the published table.

Australian cornice profiles

Blade for the material

Getting the cut you calculated

• ▸SAFETY, read this before the angles. A mitred offcut is a wedge trapped between the blade and the fence, and it is the classic drop saw ejection case. Let the blade come to a complete stop before you raise the head, every cut, no exceptions: the manual says always let the blade come to a full stop before raising the arm, and keep your hands in position until the trigger is released and the blade has stopped. Clamp the workpiece rather than hand holding it. Clamp anything that would put a hand within 152mm of the blade, and do not perform any operation freehand, meaning with the piece not supported by both the table and the fence. Keep both hands at least 150mm from the blade and never cross an arm over it. Cut short pieces off a long board against a stop block instead of holding a short piece. The DWS780 manual does not print a minimum workpiece length, so we are not going to invent one, but its own labels say clamp small pieces before cutting, and a cornice return or an architrave head is exactly the size it means. Check the lower guard closes freely before each session, make a dry run with the power off before any new setting, and wear eye, hearing and respiratory protection.
• ▸Check the saw is square before you trust any calculated number. Corrected from the research draft, which said a 1 degree fence error opens about a 6mm gap on 125mm crown. That 6mm is an imperial rounding of a quarter inch on 5 inch crown, and it belongs to a different cause, a 3 degree spring angle error, not to fence squareness. The fence arithmetic is this: a fence 1 degree out of square puts 1 degree into each half of the joint, so 2 degrees across the mitre, and 125mm multiplied by tan 2 degrees is about 4mm of open joint. Call it 4mm on 125mm cornice and about 5mm on 150mm. You need roughly 170mm of face before a 1 degree fence error reaches 6mm. Either way it is visible from the doorway. Check the blade against the fence and the blade against the table before you start, including on a brand new saw, and run the manufacturer's mitre scale and bevel pointer adjustments. On a saw with crown pawls, also check the bevel pointer reads exactly 22.5 when the head is tilted fully left against that pawl, because that is the reference the crown pawls are set from.
• ▸Check the answer is a setting your saw can actually reach, before you walk to the saw. The compound numbers for sharp corners go a long way past the stops on most machines sold here. A 45 degree wall angle needs a mitre of 56.07 at 38 degree spring, 59.64 at 45 degree spring and 62.27 at 52 degree spring, and bevels of 46.72 and 40.79. A DWS780 reaches 50 degrees mitre left and 60 right, and 49 degrees bevel both ways. A Makita LS0816F reaches 47 degrees bevel left and only 2 degrees right. So a 56 or 59 degree mitre is unreachable on the left of almost every saw here, unreachable either way on most 216mm sliders, and a 46.72 bevel is past the 45 degree stop on any single bevel saw. Treat about 45 to 50 left and 57 to 60 right as the mitre ceiling and 45 to 49 as the bevel ceiling unless you have checked your own. When the answer is out of range, do not force the head past a stop and do not freehand it. The nested fallback does not save you either, because a 45 degree wall angle nested needs 67.5. The real fallbacks are a hand mitre box or a purpose built jig, cutting the corner in two passes, or a corner block.
• ▸Zero on the mitre scale means a square crosscut, and a 45 degree mitre reads 45. DeWalt describes mitre crosscuts as made with the mitre arm at some angle other than zero, settable anywhere from zero to 50 degrees left or 60 degrees right. Wayne Drake names the two scale types: the complement of the face angle scale, which starts at 0 and runs to 45 or more both ways, is what every modern saw uses, while the older face angle scale started at 90 and ran down to about 45. That difference is the whole reason the folk rule, measure the corner and halve it, gives the wrong answer on an out of square corner. On a 0 start scale the setting is (180 minus the wall angle) divided by 2.
• ▸Bevel means the blade tilting out of vertical, mitre means the table rotating. Bevel direction matters when you buy. The Makita LS0816F sold at Bunnings bevels 47 degrees to the left but only 2 degrees to the right, which makes it a single bevel saw in practice: to cut the opposite hand of a compound joint you have to flip the workpiece end for end, and for cornice that means the ceiling edge ends up where the wall edge was, so re-mark it before you cut. A dual bevel saw such as the DWS780, 49 degrees left and right, lets you cut both hands without flipping, which is the main reason people buy them for crown work. None of this matters for plaster cornice, which is cut nested with the bevel at 0 all day.
• ▸Detents, also called positive stops or latch points, are the spring loaded notches at common angles. The DWS780, sold here as the DWS780-XE, has mitre detents at 0, 15, 22.5, 31.6, 45 and 60 degrees and bevel stops at 0, 22.5, 33.86, 45 and 49. The 31.6 mitre and 33.86 bevel detents exist for one job only, cutting American 52/38 crown lying flat. The bevel pawl is reversible: flip it so the 30 degree text faces up and the saw stops at 30 for 45/45 crown instead, which is a manufacturer level confirmation that 45 degree spring crown at a square corner needs a bevel of exactly 30.00. For Australian work those factory detents are mostly decoration. Plaster cove is cut nested at mitre 45, bevel 0, where the 45 detent is the only one you touch. The 35.26 and 30.00 pair is for 45/45 TIMBER crown lying flat, and 35.26 has no detent on any saw, so it has to be set by eye between the 35 and 36 marks.
• ▸Compound versus sliding compound. A compound mitre saw rotates for the mitre and tilts for the bevel, but the head only drops, so crosscut width is limited to roughly the blade diameter. A slider adds rails so the head pulls out and pushes through, which is what buys the width. The Australian numbers: a 216mm Makita slider crosscuts 65 x 305mm at 0 degrees and 65 x 215mm at 45, a 254mm Ozito slide reaches 320mm wide in one pass, and a 305mm DeWalt slide manages 112mm high by 231mm wide, or 349mm wide at 76mm high. Corrected from the research draft, which claimed a non sliding 254mm saw cannot take 90mm cove nested because its crosscut width is about 150mm. Crosscut width has nothing to do with it. See the next note.
• ▸Nested cornice capacity is set by how far the cornice stands up the fence and out across the table, not by crosscut width. A cove sits at 45 degrees, so it occupies its nominal size divided by root 2 in each direction: about 39mm for 55mm cove, 53mm for 75mm and 64mm for 90mm, plus whatever packer you put behind it. Any 254mm saw clears all three without thinking about it, and the DWS780 is separately rated to hold 171mm of moulding vertically against the fence at a 45 degree mitre. The saw to watch is a 216mm machine: the Makita LS0816F is 65mm high at 0 degrees, so a 90mm cove nested at 64mm is right on the limit with nothing left for a packer. Capacity also falls the moment you angle the saw, which is why the DWS780 goes from 112 x 231mm at 0 degrees mitre to 112 x 147mm at 45. You only move to a flat compound cut when the moulding is too wide to sit nested, and for Australian cove that essentially never happens. It is also the wrong move for plaster cornice in any case, since cove has no flat back to lie on.
• ▸Kerf allowance when cutting to a pencil line. Australian 254mm blades run roughly 2.6mm kerf thin and about 3mm standard, and 300 to 305mm blades about 3 to 3.2mm on a 2.2mm plate. Always cut on the waste side of the line, so the whole kerf sits outside your mark rather than straddling it. DeWalt's technique for hitting a line exactly is to match the angle as close as you can, cut deliberately a little long, then measure from the pencil line to the cut edge to work out which way to nudge the mitre before recutting. For cornice there is a trap: the waste side flips between the internal and the external cut of the same corner, so work out which piece you are keeping first and then decide which side of the line to cut. With a 3mm kerf on a 39mm drop, one cut on the wrong side of the line is most of a visible gap. Cut the first piece of any new corner at least 25mm long.
• ▸Saw scales are in whole or half degrees and compound answers are not, so a calculator has to say how to set them. Wayne Drake's guidance is to interpolate by eye: if the answer is 32.8 degrees set the pointer about 80 percent of the way between 32 and 33, and do the same for the bevel. He publishes to one decimal rather than rounding, because rounding makes a 93 degree corner and a 94 degree corner look identical, both 30 mitre and 33 bevel, when they are genuinely different settings. Print the fraction next to the number rather than making the user work it out: 33.86 sits 86 percent of the way from 33 to 34, 35.26 sits about a quarter of the way from 35 to 36. Then cut a test piece, because the pointer is only as honest as the last time you checked it.
• ▸Reflex and external corners. An external corner can be entered as its reflex angle and the arithmetic still works: 267 degrees gives a mitre setting of 43.5, because 360 minus 267 is 93 and (180 minus 93) divided by 2 is 43.5. The sbebuilders tables pair every corner with its reflex partner in the same row, which is the right model here: a 90 degree and a 270 degree corner take identical mitre and bevel settings and differ only in which side of the cut you keep. Say that out loud in the output, because keeping the wrong side of the cut is a more common error than getting the angle wrong. For 45/45 timber crown cut flat, the external 90 degree case, reflex 270, is mitre 35.26 and bevel 30.00, the same as the internal, and external 135, reflex 225, is 59.64 and 40.79, which is past the mitre range of most saws.
• ▸Cornice mitre boxes are a fixed 45 degree tool and that is a feature. Australian cornice mitre boxes are construction grade plywood, 20mm sides and base, glued, with steps in the base for 55, 75 and 90mm cornice, and they cut at 45 degrees only. Because a nested cut at a square corner is 45 degrees regardless of spring angle, one box handles every profile in the Australian range. The corollary is that a plain box cannot handle an out of square corner at all, which is exactly where a drop saw or a calculator earns its keep. For bays and splayed corners there are dual cut boxes that add the 135 degree slot: Wallboard Tools make one in plywood for 55, 75 and 90mm cornice, and Intex sell a plastic dual box at Bunnings covering 55, 90 and 135 degrees for the same three sizes. That claim was unsourced in the research draft and is now sourced.

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How it is done here

The short answer for Australian cove cornice, before anything else

Square corner, any Australian cove, any size, any brand: mitre 45 degrees, bevel 0, cut in position in a cornice mitre box or nested against the fence of a drop saw. Out of square corner: mitre (180 minus the measured wall angle) divided by 2, bevel still 0. An 87 degree corner is 46.5, a 93 degree corner is 43.5. The spring angle changes neither number. That is the whole reason one 45 degree cornice mitre box handles 55, 75 and 90mm cove and every decorative profile in the range as well. Spring angle only matters if you are cutting the cornice lying flat on the saw table, and you should not be doing that with plaster cornice at all.

Cornice goes in the box upside down and backwards, and that is the Australian default

CSR's instruction is blunt: when using a cornice mitre box the ceiling edge is always placed along the bottom of the box, and the cornice must sit square to the base and the side, packed if necessary. The base of the box is standing in for the ceiling and the side is standing in for the wall, so the piece sits inverted and reversed from the way it will hang. DeWalt describes exactly the same position on a drop saw: the bottom of the moulding, the part that goes against the wall, against the fence, with the top of the moulding resting on the table, and the angled flats on the back resting squarely on both. Before you cut anything, pencil CEILING on one edge and WALL on the other, and always mark your length on the wall edge. If you pack the piece to stop it rocking, use the same packer for every cut on the job, because a packer that moves changes the angle.

Never cut plaster cornice lying flat, and what the flat compound numbers are actually for

Plaster cornice is always cut in position, never lying flat. DeWalt's own precondition for the flat compound method is that the moulding lays flat with its broad back surface down on the saw table, and a cove has no broad flat back, only two narrow lands at the edges. Laid face up it rests on two thin lines, rocks under the blade, and cannot be held as the same manual demands: never make any cut unless the material is secured on the table and against the fence. CSR's install guide never mentions a compound or flat cut for cornice at all, only a fine tooth saw with a Mitremasta or a cornice mitre box. The flat compound figures belong to timber and MDF crown mould, which does have a flat back. For those, at a square corner, 45/45 crown needs mitre 35.26 and bevel 30.00, and American 52/38 crown needs mitre 31.62 and bevel 33.86. If you are cutting timber crown mould, measure its spring angle first. No Australian supplier publishes one for the primed pine cornice mould sold in hardware stores, so the label is not a substitute for a bevel gauge.

Which end of the cut to keep, which is a more common mistake than getting the angle wrong

Nested, with the ceiling edge on the table and the wall edge against the fence, DeWalt publishes the whole table. Piece running along the left hand wall: internal corner, mitre right 45, save the right side of the cut. External corner, mitre left 45, save the right side. Piece running along the right hand wall: internal corner, mitre left 45, save the left side. External corner, mitre right 45, save the left side. The pattern is worth memorising: on the left hand wall you always keep the right piece, on the right hand wall you always keep the left piece, whatever kind of corner it is. Australian cornice guides label the four cuts IL, IR, EL and ER, internal left, internal right, external left, external right, and CSR prints a diagram of each. For timber crown cut flat, 52/38 only: left wall internal is bevel left 33.9 with the mitre table right 31.62, save the left end. Left wall external is bevel right 33.9, mitre left 31.62, save the left end. Right wall internal is bevel right 33.9, mitre left 31.62, save the right end. Right wall external is bevel left 33.9, mitre right 31.62, save the right end.

Internal and external cornice corners, which edge runs long

At an internal corner the ceiling edge is the shorter one, so the cut leaves the ceiling edge short and the wall edge long, and you reverse the cut direction for the other side of the same corner. At an external corner it is the other way round, the wall edge is short. Knauf and USG Boral state the same rule as a measuring convention rather than a cutting one: measure internal corners to the long point, which is the wall edge, and external corners to the short point. Same cut, different way of saying it. Two brands, one rule, and no reason to think they need opposite cuts. On a 55mm cove the ceiling edge finishes about 39mm short of the wall edge at an internal corner, which is also how far out your guide line will be if you strike it at 55mm instead of 39mm.

Where to strike the guide line on the wall, and why cove is different

CSR tell you to mark the wall guide line at a distance from the ceiling equal to the size of the cornice, using 75mm for Gyprock Aria as their worked example. That is right for a flat or stepped profile, and wrong for cove, because cove runs on the diagonal. Cove drops its nominal size divided by root 2: a 55mm cove drops about 39mm, a 75mm cove about 53mm and a 90mm cove about 64mm. Strike a 90mm cove line at 90mm and you are 26mm out, the cornice will not reach it, and you will have chased a line down four walls before you notice. The safest method on any profile is to hold an offcut into the corner, mark where the bottom edge lands, and use that.

Out of square corners, and the folk rule that gets it backwards

Measure the actual corner with a digital angle finder or a sliding bevel, do not assume 90. Then on any modern drop saw the setting is (180 minus the wall angle) divided by 2. An 87 degree corner needs 46.5 on each piece, a 93 degree corner needs 43.5. This is the single most common arithmetic mistake in trim work, because the folk rule everyone repeats, measure the corner and halve it, is only correct on the older style of saw whose scale starts at 90 and counts down. Every saw sold today has a scale that starts at 0 and runs both ways, so you subtract from 180 first and then halve. Wayne Drake's worked example is an inside 93 degree corner giving 43.5, not 46.5. This rule is for nested or upright cutting only. Timber crown lying flat needs the full compound calculation. Intrim's low tech version for site work is to stand an offcut in the corner, note the real angle, and split the cuts unevenly, say 43 and 47 rather than 45 and 45.

Walls that lean, which is a different problem from walls that are out of square

Everything above assumes the corner is square in the vertical plane as well as in plan. In older Australian brick and timber framed stock, and in Queenslanders in particular, walls lean. A wall out of plumb changes the effective spring angle along the run, and an external corner that is out of plumb will open a flat 45 degree skirting mitre at the top even when the plan angle is a perfect 90. Two things follow. Check the corner with a level before you cut, and check it at cornice height rather than at eye height or down on the floor, because that is where the cornice is going. If the corner leans, an external skirting mitre becomes a compound cut: keep the mitre at (180 minus the plan angle) divided by 2 and tilt the bevel by the lean angle. At the very least, when a plan-perfect mitre still gaps at one end, this is what you are looking at.

Measuring a corner when you do not own an angle finder

Hold two offcuts into the corner so each one beds against its own wall, scribe along both onto the floor or onto a piece of card, and bisect the marked angle. Or set a sliding bevel into the corner, lock it, and lay it on a printed protractor. Either way you end up with the real wall angle, which is the number the calculator wants. Do the bisect at cornice or skirting height, not at whatever height is comfortable, and remember the point above: the answer is (180 minus that angle) divided by 2, not half of it.

Bay windows and splayed corners

An Australian canted bay is normally set out on a 45 degree splay, which gives a 135 degree internal wall angle and a 22.5 degree mitre on each meeting piece of skirting or architrave. The other two common splays are 30 degrees, giving a 150 degree wall and 15 degree mitres, and 60 degrees, giving a 120 degree wall and 30 degree mitres. For cornice in the same bay, cut in position, it is the same arithmetic: (180 minus 135) divided by 2 is 22.5, bevel 0. A standard Australian cornice mitre box only cuts 45, so a bay needs either a dual cut box with the 135 degree slot, which Wallboard Tools and Intex both sell for 55, 75 and 90mm cornice, or a drop saw. Cut the short bay returns last and leave them at least 25mm long, because a short piece that is short is scrap.

Regular polygons, planters and frames, including the 22.5 degree octagon

For a regular shape with equal sides the setting is 180 divided by the number of sides. Three sides 60, four sides 45, five sides 36, six sides 30, seven sides 25.7, eight sides 22.5, nine sides 20, ten sides 18, twelve sides 15. DeWalt prints this table and adds the caveat that decides whether your planter box closes up or not: 180 divided by n is the MITRE if the material is cut standing vertically against the fence, and the BEVEL if it is cut lying flat. Get that the wrong way round and an octagon comes out as a very neat pile of firewood. Two 22.5 degree cuts make the 45 degree turn and close the 135 degree internal corner, which is why the octagon number and the bay window number are the same. For setting out, side length from the internal across-flats width W is W multiplied by tan(180/n): 0.7265 x W for a pentagon, 0.5774 x W for a hexagon, 0.4142 x W for an octagon. Allow 10 per cent waste and cut one test joint first.

Scribing internal corners on skirting instead of mitring them

Scribing is the professional standard for internal corners on skirting, because a scribed joint will not open as the timber moves and it copes with a wall that is not 90 degrees without any adjustment. The Intrim method, from an Australian moulding manufacturer: run the first board square into the corner. On the second board swing the MITRE TABLE to 43 degrees with the blade vertical, bevel 0, and cut across the face to reveal the profile line. Cut it as an internal mitre, so the back of the board stays long and the face is the short point. If the face came out longer than the back you have cut the wrong hand and the revealed line is useless. Pencil the line where the mitre face meets the skirting face. Back cut the flat section at mitre 90 with about 5 degrees of tilt to undercut it, then cope the curved part with a coping saw held angled backwards. Test fit and take high spots off with a half round file. Intrim also notes internal scribe joints always land on the left hand end of the board when you work left to right clockwise from the door opening. Note the wording trap: Intrim's own summary elsewhere says tilt the saw to 43, which reads as a bevel. It is the table, not the tilt.

External corners on skirting, architrave corners, and return ends

External corners on skirting are mitred, not scribed: 45 degrees on both pieces, PVA on the mitre faces, then cross nail through the joint so it cannot open. Architraves are mitred at every corner. A door gives you two legs and a head: the bottom of each leg is cut square where it meets the floor or the skirting block, the top is a 45 degree mitre. Measure between the corner quirk points, which is the short length of the mitre, and add 5mm. Run a consistent quirk, normally 5mm, and Intrim are explicit that a consistent quirk matters more than a perfect mitre, because the eye follows the quirk line and not the joint. Windows take four pieces, worked anticlockwise from the right hand side. Glue every architrave mitre. Where skirting or architrave stops in mid air, at an opening or a hob, close the end with a mitred return: cut the run at 45, then cut the small triangle off the same board's 45 and glue it on, so the profile wraps round instead of showing raw end grain or bare MDF core. Cut that triangle off a long board with a stop block, never as a loose offcut held by hand.

Out of square door jambs, which is not the same as an out of square wall

Check the jamb with a square and note the real angle, then adjust the architrave mitres to suit, 43 and 47 rather than 45 and 45. The two pieces have to add up to the real angle but they do not have to be equal halves, and it is usually better to split the error unevenly so the quirk stays constant down both legs. A consistent 5mm quirk reads as a straight line from across the room. A joint that is half a degree off does not.

Long point, short point, and how much length a mitre adds

On any mitred end the long point sits past the short point by the material thickness multiplied by tan(mitre). On 18mm skirting at a 45 degree external corner that is 18mm. In a bay at 22.5 degrees it is only 7.5mm. That is the number you need whenever a source says measure to the long point and does not say how much longer that is. For cornice, measure to the wall edge at an internal corner and to the ceiling edge at an external one, and cut the first piece of every new corner at least 25mm long, because a mitre that is 1mm short at the ceiling cannot be recovered and a mitre that is long can.

Raked and cathedral ceilings, which this calculator does not cover

On a rake the cornice sits on the ceiling exactly as it would if the ceiling were flat, so the discrepancy shows up on the wall and not on the ceiling, which means a bigger gap to fill at the bottom of the run than at the top. Here is the part that matters and that most write-ups leave out: the profiles genuinely do not match at a rake. A stock cove run up the rake cannot mitre cleanly into the same stock cove on the level run. Either the level run has to be rolled or tipped out of position, which distorts it, or a second profile has to be developed for the raking piece. That is why the Australian fix is what it is, a 45 degree cut with the gap filled in finishing compound, or the raking cornice fitted first and the bottom of the lower run kicked out with about 5mm left to fill. It is not a bad habit, it is what a stock profile allows. A rake corner is also a horizontal turn and a vertical turn at the same corner, so it is not one angle, and this calculator does not handle it. Work from a ceiling slope table or order a raking profile. If your pitch is given as a ratio, degrees equals atan(rise divided by run), so 1 in 20 is 2.9 degrees and 1 in 10 is 5.7 degrees.

Square set and shadowline junctions have nothing to mitre

If the wall meets the ceiling in a square set or a shadowline bead there is no sprung cornice, no spring angle and no compound mitre. The corner is formed with steel or aluminium trim beads and set in compound, not cut on a saw. Do not look for an angle here, and be careful of any calculator that hands you one: feed a 0 degree spring angle into the compound formulas and they return a confident mitre of 0.0 and a bevel of 45.0, which is a real-looking answer to a question that does not exist.

Bowed and wavy walls, uneven floors, and bowed timber

Even in new Australian homes a flat wall and a level floor are rare. Intrim's ranked fixes for a wavy wall: scribe the skirting to the wall profile with a compass or scribe tool, fill with adhesive for minor undulation up to 3mm, pack low spots with timber shims, or use flexible polyurethane skirting for a genuinely curved wall. For a gap under the skirting where the floor is not level: scribe to the floor, which is best on solid floors, fit quad or scotia over it, or caulk variation up to 3mm. There is a specific Australian plasterboard problem worth naming, skirting dip, where the board tips inward at the bottom because it sits in the recessed edge of the sheet. Drive screws into the studs at skirting height so the heads sit flush with the main wall surface, then let the skirting bear on the screw heads instead of sinking into the recess. On brick and masonry, mark the fixings by driving a nail through the skirting face, drill 5mm holes, plug them flush, and use construction adhesive plus screws, with finger jointed pine rather than MDF because MDF does not hold fixings as well. Separately, the timber itself: a bowed board must go on the saw so the bow cannot close on the blade near the end of the cut. DeWalt prints a right way and a wrong way for this. Set it up wrong and the cut pinches the blade and the piece kicks.

Test cut on scrap, every time, before the real length

Both the manufacturer manual and the compound mitre reference say this in capitals. DeWalt: the angles for crown moulding are very precise and difficult to set exactly, they shift easily, and very few rooms have exactly square corners, so pretest with scrap. Australian cornice guides say check each cut piece for actual fit before you mix any cornice cement, and pre cut everything to length before you mix, because cornice cement has a working life of only about 60 minutes. Once the cement is going off you will accept a joint you would have recut ten minutes earlier.

Fitting the last piece and springing the mitres in

Install the shorter lengths of cornice first, then fit the longer lengths by bowing them out to spring the mitres into place. Butter all mitres and butt joints with cornice adhesive before pushing them home and clean the excess off straight away with a broadknife and a cornice tool, because set cement comes off with a chisel and takes the paper with it. Temporary nails along the top and bottom edges hold the run while the cement sets, a minimum of 20 minutes of support, and CSR say leave it at least two hours before you pull the nails.

Measure every corner, and measure the moulding too

Do not trust the label on the moulding. Wayne Drake documents stock labelled 52/38, which implies a 38 degree spring angle, that was actually 45/45, and warns that some crown labelled 38 or 45 is undercut at the factory by up to 3 degrees, giving a real spring angle of 35 or 42. Three degrees of spring angle error moves the mitre and the bevel by 1.5 to 1.8 degrees each, and on a 125mm face that is a visible gap at the ceiling, about a quarter inch in Drake's own words on 5 inch crown. Corrected from the research draft, which said about 1.5 degrees: 1.5 is the floor, not the typical figure. He also makes a point that trips people up, that a moulding has two spring angles depending on which edge you decide is the bottom, so measure it the way the piece will actually hang. Method: hold the bottom edge of the moulding flat against a straight edge standing in for the wall and measure from the back of the moulding to that straight edge, or measure the angle at the back of the piece and subtract from 180. None of this applies to plaster cove, which is cut nested where the spring angle drops out of the sum entirely.