Calculator
Crown Moulding Calculator
A room's crown is not one long ribbon wrapped around four walls — it is four separate runs, and each one has to come from a stick long enough to cross that particular wall in one piece, because a splice partway along an unbroken length of trim reads as a visible seam. Dividing the room's total perimeter by the length of stock you buy answers a different question than a shopping list needs answered: it tells you the footage crossed, not how many individual sticks actually reach across each wall once a mitre or a cope is left at both ends.
This calculator allocates a stick to each wall in turn, holds back a small allowance at each end for the two cuts, and only then adds the sticks together. The number it returns is usually higher than perimeter divided by stick length, and this page prints both figures side by side so the gap between them is visible before you are standing at the lumber yard short a length.
Calculate your quantity
Crown is cut upside down and backwards; leave room to redo one.
For bays, alcoves and L-shaped rooms.
Sticks to buy
4 16 ft sticks
- Room perimeter
- 52 lin ft
- Walls to run
- 4 walls
- Sticks if you just divide the perimeter
- 4 sticks
- Offcut left over
- 8 lin ft
- Inside corners
- 4 corners
- Coped joints
- 4 cuts
- At these wall lengths the per-wall allocation and the perimeter shortcut agree.
Shopping summary
- • 4 x 16 ft lengths of crown moulding
- • 1 tube(s) of trim adhesive and a box of 2 in finish nails
This is an estimate — confirm structural work with a professional.
How this calculation works
The room is treated as four walls — length, width, length, width — plus one entry for every extra segment you add for a bay, a closet return or an L-shaped jog. Each wall's requirement is its own length plus the cut allowance doubled, because both ends of every wall meet a corner or a return and each of those gets a fresh cut. That requirement is rounded up to the next whole stick, one wall at a time, and the sticks are summed afterward.
That order of operations — round per wall, then add — is not the same arithmetic as adding the raw wall lengths and rounding once at the end, and the difference is the whole reason this page exists rather than a five-second division. A wall that needs 12.6 feet of stick still buys a full 16-foot length past 12 feet, and the leftover 3.4 feet is not credited toward the next wall's requirement, because in practice it almost never reaches across a second wall once its own cut allowance is spent.
- Every wall's requirement rounds up independently — a wall a few inches over a stick length still buys the next whole stick, and that excess becomes offcut rather than credit toward another wall.
- The cut allowance is charged at both ends of every wall, not only at the two ends of the room, because every wall meets a corner or a return at each end and gets its own cut there.
- A short added segment — a bay, a closet return, a jog — can cost nearly a full stick on its own. Rooms with more corners open a wider gap between the per-wall total and the perimeter shortcut than rooms with more raw footage do.
- Nothing here assumes you can reuse an offcut from one wall on another. If your installer plans to fit a short return from a longer wall's leftover, that is a field decision this page deliberately does not make for you.
The formula
sticks = the sum, over every wall, of ceil((wall length + 2 × cut allowance) ÷ stick length)
- wall length
- Each of the room's four sides in turn, plus one entry per extra segment for a bay, closet return, or jog in an L-shaped room — every segment gets its own line in the calculation rather than being folded into the perimeter.
- cut allowance
- Inches held back at each end of a wall for the mitre or cope cut. It is added twice per wall because both ends of every wall terminate at a corner or a return, not just the two ends of the room.
- stick length
- The stock length you are buying. Crown is milled and sold in fixed lengths — commonly 8, 10, 12 and 16 feet — not cut to order, so this is a choice among what a supplier actually stocks rather than a free number.
- extra walls / extra wall length
- Additional short runs beyond the room's basic rectangle, each entered separately because each needs its own stick regardless of how short it is — a 3-foot return costs the same rounding penalty as a 13-foot wall.
Rounding each wall up separately and then adding the sticks is not the same arithmetic as adding the wall lengths and rounding once — the first is how a room is actually cut and delivered, the second is how a rough perimeter estimate gets made on the back of an envelope. The gap between them grows with the number of corners in the room, not with the room's raw square footage.
Where these numbers come from
- 8, 10, 12 and 16 ft stock lengths
- Trade convention. Crown manufacturers mill and ship standard-line MDF and finger-jointed profiles in these lengths near-universally across North American suppliers; a specific order can be milled longer, but off-the-shelf stock does not run past 16 ft in most yards.
- 6 in cut allowance per end
- Working default from finish-carpentry practice rather than a manufacturer spec: enough to true up a first cut, redo a coped joint that doesn't seat cleanly, or absorb a corner that isn't quite 90 degrees. An installer confident on a square room can trim this back; a first attempt at a coped inside corner is worth keeping the full allowance.
- 1 tube of adhesive per 6 sticks
- Derived on this page as a rough purchasing rule from typical bead coverage on a standard adhesive tube against an average stick length — used only to size the shopping list, not a substitute for the coverage figure printed on your own adhesive's label.
- One coped joint per inside corner
- Standard finish-carpentry practice: outside corners are mitred, inside corners are coped rather than mitred because seasonal wood movement opens an inside mitre into a visible gap over a heating cycle. The count here is a planning proxy, not a substitute for walking the room and marking which corners are actually inside versus outside.
Worked examples
A plain 14 by 12 foot bedroom, stock crown in 16 ft lengths
| Room length | 14 ft |
|---|---|
| Room width | 12 ft |
| Moulding length sold | 16 ft |
| Allowance per cut end | 6 in |
| Extra wall segments | 0 |
| Extra wall length | 0 ft |
| Sticks to buy | 4 16 ft sticks |
|---|---|
| Room perimeter | 52 lin ft |
| Walls to run | 4 walls |
| Sticks if you just divide the perimeter | 4 sticks |
| Offcut left over | 8 lin ft |
| Inside corners | 4 corners |
| Coped joints | 4 cuts |
At 16-foot stock, every wall in this room — two runs of 14 feet and two of 12 — needs only a single stick each, so the per-wall total and the perimeter shortcut land on the same number: 4 sticks either way, with 8 feet of the 64 feet you bought left over as offcut. A rectangular room whose walls each fit comfortably inside one stick length is the one case where dividing the perimeter happens to give the right answer, which is exactly why it is tempting to rely on that shortcut everywhere else.
That 8 feet of offcut is spread across four pieces, so none of it is a single reusable length — closer to 2 feet per wall once the cut allowance is subtracted, which is not enough to fit a return or a small closet elsewhere in the house. Treat it as scrap, not as inventory, unless one wall happened to leave an unusually clean remainder.
A 15 by 15 foot square room with a small closet return, in 12 ft sticks
| Room length | 15 ft |
|---|---|
| Room width | 15 ft |
| Moulding length sold | 12 ft |
| Allowance per cut end | 6 in |
| Extra wall segments | 2 |
| Extra wall length | 4 ft |
| Sticks to buy | 10 12 ft sticks |
|---|---|
| Room perimeter | 68 lin ft |
| Walls to run | 6 walls |
| Sticks if you just divide the perimeter | 6 sticks |
| Offcut left over | 46 lin ft |
| Inside corners | 6 corners |
| Coped joints | 6 cuts |
Here the two numbers separate hard: 10 sticks against a perimeter shortcut of 6, two-thirds more than the naive figure suggests. The four 15-foot walls account for 8 of those sticks, each needing a second 12-foot length past the first because 15 feet plus a foot of cut allowance clears 12 feet. The other 2 sticks belong entirely to a pair of 4-foot closet returns — each one barely a third of a stick's length, and each one still costing a full stick because the rounding rule does not care how short the remainder is.
Buying to the perimeter number here would leave the installer four sticks short, and every bit of that shortfall traces to two returns that look like almost nothing on a tape measure. The 46 feet of offcut on 120 feet of stock — nearly 40% — is driven mostly by those same returns; an installer experienced with coping could likely fit at least one of them from a main wall's leftover and save a stick, but this page prices the safe, buyable number rather than a field improvisation.
Common mistakes
- Buying to the perimeter total instead of the per-wall total. The two only agree when every wall fits inside one stick length; add a bay, a return, or a wall just over a stick's length and the perimeter number under-orders.
- Cutting a piece to the exact tape measurement with no cut allowance, then finding a coped joint that will not seat or a corner that was never quite square to begin with.
- Treating a bay window or closet return as extra footage rather than extra sticks. A 3-foot return costs a whole stick, the same rounding penalty as a 13-foot wall, because both round up to the next full length.
- Assuming a wall's leftover will cover a second, shorter wall. Coping needs enough extra length on the piece being fit to the profile in front of it, and once a stick is committed to one wall's cuts, what remains is rarely long enough for a fresh run elsewhere.
- Mitring an inside corner instead of coping it. Crown is thick enough that seasonal wood movement opens an inside mitre into a visible gap by the next heating season, while a coped joint rides the movement without opening.
Shopping summary
Order the sticks-to-buy figure, not the perimeter figure — on any room with a return or a bay, the difference between the two is real material rather than padding. Round to whole sticks in the length you chose, since suppliers do not sell crown by the running foot cut to order.
Crown's overage here comes from rounding to whole sticks, not from a percentage held back for breakage — for materials that are genuinely ordered against a waste percentage, the waste factor calculator is the right tool for that question rather than this one. If the same room is getting floor-level trim as well, price it separately with the baseboard calculator: baseboard and crown are milled to different profiles and almost never share a stick even when they're bought from the same supplier run.
Also worth having on the truck: adhesive tubes at roughly one per six sticks, a box of finish nails, wood filler for the nail holes, and paintable caulk for the seam where the moulding meets a ceiling that is not perfectly flat. If the room is also getting door or window trim in the same visit, the door and window casing calculator works out that stock on its own logic — legs and heads per opening, not runs and corners per wall.
FAQ
Why does this page's stick count come out higher than what my supplier quoted from my room's total footage?
Because a quote built on total footage divides once at the end, while an actual order is cut wall by wall. Every wall that needs even a sliver past a whole stick buys the next one, and those slivers do not average out the way a single perimeter division assumes — the gap is largest in rooms with several short walls or returns, smallest in a plain rectangle where every wall happens to fit one stick.
Can I save a stick by cutting my shortest wall from another wall's offcut?
Sometimes, but only if the offcut is longer than the short wall's requirement plus both of its cut allowances after the main wall's own cuts are made — not just longer than the wall itself. A return under about 3 feet paired with a main wall that left 4 feet or more of clean offcut can often work; anything tighter than that is a bet you're making on-site, which is why the calculator prices fresh stock per wall rather than assuming a save that depends on how the first cuts land.
Does the cut allowance need to be the same at an outside corner as an inside one?
In practice, no — an outside mitre is usually a more forgiving cut than a coped inside joint, and a confident installer can trim the allowance on outside-corner-only walls. The calculator applies one figure everywhere because most rooms mix both corner types on the same wall, and a cut that comes up short is equally ruined whichever kind of corner it was headed for.
What if my room has a bay window or isn't a plain rectangle?
Use the extra wall fields to add each additional segment as its own length. Give those segments a slightly larger allowance than the default if you can — a bay return often meets the main wall at an inside corner on one end and an outside corner on the other, which puts two different joint types on a single short piece instead of the one type a straight wall usually gets.
Should I buy one extra stick if this is my first time coping a joint?
Yes, if coping is new to you. The most common failure on a first attempt is cutting the coped profile a hair proud, so the piece sits long against the adjoining moulding — the fix is a fresh cut from new stock, not a re-scribe, since crown removes almost no material per pass without changing the profile's shape. One spare stick is cheap insurance against redoing a whole wall.
Is crown moulding measured the same way as door or window casing?
No. Crown runs continuously around a room and is priced per wall the way this page does it; casing wraps individual openings and is priced per leg and head instead, which is why it has its own casing calculator rather than sharing this one's arithmetic. The failure modes differ too — crown's risk is an uncoped inside corner, casing's is a reveal that doesn't leave a mitre able to close.
Where to go next
The projects this number is a step of, the guides that explain the method behind it, and the rest of its trade group.