A Free Tool · Baseboard, Crown & Chair Rail · Linear Feet
How much baseboard do you actually need?
Enter a room's length and width — or its perimeter directly — subtract the
door openings, add a little waste for miter cuts, and get the total linear feet of trim
plus the number of pieces to buy at 8, 12, or 16 ft stock lengths. The same math works
for baseboard, crown molding, and chair rail.
Linear feet & pieces to buy·Room size or direct perimeter·Baseboard / crown / chair rail
Read this first
These are estimates based on your measurements and a waste factor, not a substitute for
walking the room with a tape measure. Always buy a little extra — running short by
one stick mid-install means another trip to the store and a possible color or profile
mismatch on the new lot. Subtract doorways for baseboard, but remember that crown and
chair rail often run past doors. Confirm the actual stock lengths and per-piece price at
your store before buying.
The calculator
Estimate linear feet and pieces
Pick how you want to enter the room (length × width, or a perimeter you already measured), subtract your door openings, set the waste percentage, and choose the stock length sold at your store. You'll get total linear feet and how many pieces to buy.
Perimeter is figured as 2 × (length + width).
Add up every wall the trim runs along — best for L-shapes and bump-outs.
Doorways the trim does not cross. Use 0 for crown or chair rail that runs over the door.
A standard interior door with frame is about 3 ft. Measure wider or double doors.
10% for a straight room; 15% for many corners or mitered crown.
Trim is sold in fixed lengths. Longer pieces mean fewer joints.
Perimeter
Less door openings
Net length (before waste)
Waste applied
Total trim needed
Pieces to buy
The math, honestly
How the piece count is figured
It's all linear feet. Start with the perimeter — for a
rectangular room that's 2 × (length + width), or you can enter a
perimeter you measured directly. Then subtract the door openings:
perimeter − (door count × door width), using about 3 ft per
standard door.
Multiply that net length by your waste factor to cover miter cuts and
mistakes: net × (1 + waste/100). Finally, divide by the
stock length the store sells and round up, because you can't buy a
partial board: pieces = ⌈ trim ÷ stock ⌉.
A worked example: a 12 ft × 15 ft room with one 3 ft door at
10% waste, buying 12 ft trim. Perimeter is 2 × (12 + 15) = 54 ft;
net is 54 − 3 = 51 ft; with waste that's
51 × 1.10 = 56.1 ft; and pieces are
⌈ 56.1 ÷ 12 ⌉ = 5. Five sticks of 12 ft trim.
Why the waste matters: every corner is two angled cuts, a miter that
comes out wrong wastes a board end, and short offcuts rarely fill a full wall. The
waste factor is cheap insurance against a second trip to the store mid-install.
Stock lengths and pieces per 100 feet
Trim is sold in fixed lengths. Here's how many pieces each stock length takes to cover
100 linear feet of wall, so you can see how the longer boards cut down on joints and
trips down the aisle. These are the lengths the calculator offers.
Stock length
Pieces per 100 ft100 ÷ length, rounded up
Best for
8 ft
13
Small rooms, closets, tight transport
12 ft
9
Most rooms — the common default
16 ft
7
Long walls, fewest joints, hard to haul
Pieces-per-100 ft is 100 divided by the stock length, rounded up to whole boards. In a
real room you won't get perfect use out of every stick, which is exactly what the waste
factor accounts for.
How much waste to add
The right waste percentage depends on how many cuts the job involves. More corners and
compound miters mean more wasted board ends. Use this as a starting point and round up
when in doubt.
Job type
Suggested wasteadded to net length
Why
Straight baseboard
10%
Few corners, simple square cuts and butt joints
Lots of corners
15%
Many inside/outside miters waste more board ends
Crown molding
15%
Compound miters are unforgiving; cuts go wrong more often
Chair rail
10%
Runs the perimeter like baseboard, usually fewer doors subtracted
The calculator defaults to 10%. Bump it to 15% for crown or any room with a lot of jogs,
bump-outs, and corners. First-time installers may want a little more cushion than a pro.
Reading the result well
A linear-foot number is only useful if you act on it sensibly. Four things worth knowing
before you buy.
Subtract doors, not windows
Baseboard stops at each side of a door casing, so subtract the full opening width — about 3 ft for a standard interior door, more for wide or double doors. Do not subtract windows: baseboard runs along the floor underneath them. Crown molding and chair rail sit high on the wall and usually run past doorways, so for those you'll often subtract fewer openings, or none.
Match waste to the corner count
Ten percent is fine for a simple rectangular room with straightforward cuts. Add 15% when the room has lots of corners, jogs, and bump-outs, or when you're running crown molding on compound miters where a wrong cut wastes a whole board end. The few extra dollars of trim are far cheaper than a second trip to the store.
Buy the longest length that fits
Longer boards mean fewer seams. A 16 ft piece can span a long wall in one length where two 8 ft pieces would leave a coped butt joint to fuss with. Fewer joints look cleaner and waste less material. The trade-off is handling: 16 ft trim is awkward to transport and maneuver in a finished room, so balance joint count against what fits in your vehicle.
Buy whole pieces — and don't under-buy
You can't buy a fraction of a board, so the calculator rounds the piece count up. Keep the extra on hand until the last corner is cut; one spare stick is cheap insurance against a botched miter. Running short forces a mid-install trip, and a fresh lot may not perfectly match the profile or finish of what you started with.
Where to buy
Got your numbers? Here's where to pick up what you need:
The terms behind the calculator, in plain English. These are background definitions to
help you order the right amount — not a carpentry manual.
Perimeter
The total length of all the walls the trim runs along. For a simple rectangle it's 2 × (length + width). For an L-shaped room or one with bump-outs, you measure each wall and add them up — that's when the direct perimeter mode is easier than length × width.
Linear foot
One foot of length along the wall, regardless of the trim's height or profile. Baseboard, crown, and chair rail are all sold and measured by the linear foot, which is why the same math works for all three.
Baseboard
The trim that runs along the bottom of the wall where it meets the floor. It stops at each side of a door casing, so door openings get subtracted from the perimeter. Windows do not, because baseboard runs underneath them.
Crown molding
Trim installed at the top of the wall where it meets the ceiling, cut on compound (angled in two planes) miters. Because crown runs high, it usually continues over doorways, so you subtract fewer openings — and because the cuts are unforgiving, bump the waste to about 15%.
Chair rail
A horizontal molding partway up the wall, traditionally at chair-back height. Like baseboard it runs the room's perimeter, but it sits above door casings, so you typically subtract fewer doorways than you would for baseboard.
Stock length
The fixed length trim is sold in — commonly 8, 12, or 16 feet. You divide your total linear feet by this and round up to whole pieces. Longer stock means fewer joints, but it's harder to transport and handle.
Waste factor
The extra trim bought above the net length — typically 10 to 15% — to cover miter cuts, mistakes, and offcuts too short to use. It's cheap insurance against the costlier problem of running a stick short during the install.
Miter / cope
The angled cuts at corners. A miter joins two pieces at an angle (45° for a square corner); a cope shapes the end of one piece to fit the face of another for inside corners. Both consume board ends, which is what the waste factor is for. Longer stock reduces the number of corner joints you have to make.
Direct perimeter
Entering the total wall run yourself instead of length × width. Use this for any room that isn't a clean rectangle — L-shapes, alcoves, bump-outs, angled walls — where length times width would miss part of the wall the trim actually covers.
Frequently asked
Start with the perimeter: for a rectangular room that's 2 × (length + width), so a 12 ft × 15 ft room is 2 × (12 + 15) = 54 linear feet. Subtract the width of door openings the trim doesn't cross, about 3 ft each, then add a waste factor, usually 10%. A 12 × 15 room with one 3 ft door at 10% waste needs (54 − 3) × 1.10 = about 56.1 linear feet. Try it in the calculator.
Divide your total linear feet (waste included) by the stock length sold at the store, then round up. For 56.1 linear feet in 12 ft sticks, 56.1 ÷ 12 = 4.68, which rounds up to 5 pieces. You always round up because a partial board can't fill a full wall, and the leftover covers miter cuts.
Add about 10% on a straightforward room and 15% when there are many corners or you're running mitered crown molding. Every inside and outside corner is two angled cuts, and a miter that comes out wrong wastes a board end. Picking your longest stock length also cuts the number of joints, which means fewer cuts and less waste overall.
Yes. Baseboard, crown molding, and chair rail are all linear trim running the perimeter of a room, so the math is identical: perimeter minus openings, plus waste, divided by stock length. Crown is cut on compound miters and is less forgiving, so bump the waste to 15%. Crown and chair rail usually run past doorways above the casing, so subtract fewer door openings than you would for baseboard — often set the door count to zero.
For baseboard, yes — it stops at each side of a door casing, so subtract the full opening width (frame included), about 3 ft for a standard interior door. Do not subtract windows, because baseboard runs underneath them along the floor. For crown and chair rail, which sit well above the floor, the trim usually continues across the top of a door, so subtract fewer openings or none.
Use about 3 feet per opening as a default. A 30- or 32-inch door slab plus the jamb and casing comes out close to 3 ft of wall where baseboard doesn't run. Wider doors, double doors, and cased openings are bigger, so measure the actual opening when you can — the calculator lets you change the per-door width to match what you have.
Use length × width when the room is a simple rectangle — it's faster and the calculator doubles the sum for you. Switch to direct perimeter when the room has bump-outs, an L-shape, alcoves, or angled walls, where length times width wouldn't capture the real wall run. In that case, walk the room with a tape measure, add up every wall the trim touches, and enter that total.
Longer boards mean fewer seams. A 16 ft piece can run a long wall in one length where two 8 ft pieces would leave a butt joint to cope, glue, and sand. Fewer joints look cleaner and waste less material. The trade-off is that 16 ft trim is awkward to transport and handle, so balance joint count against what fits in your vehicle and the room.