Start with the room perimeter
For a rectangular room it is twice the length plus twice the width. For an L-shaped room or a hallway, switch to wall-by-wall mode and enter every wall run, which also produces an exact cut plan.
Baseboard trim calculator
Baseboard, molding
& trim calculator
Turn a room, or a known perimeter, into running lengths and whole sticks of baseboard, crown molding, chair rail, shoe, door and window casing and box molding — with the miter and bevel angles for every corner.
Enter measurements ↓
Based on your result
What you'll need
Each trim type is counted in whole sticks, because trim is sold by the length and offcuts rarely reach the next wall. Buy long lengths for long walls to avoid extra scarf joints.
- Baseboard
Perimeter minus doorways, in whole lengths
- Calculate above
- Shoe / quarter round
Covers the gap between baseboard and floor
- Calculate above
- Crown molding
Full perimeter at the wall and ceiling joint
- Calculate above
- Chair rail
Horizontal rail at about one third of the wall height
- Calculate above
- Door casing
Two legs and a head per cased side
- Calculate above
- Window casing
Head, sill and two legs per window
- Calculate above
- Box / picture molding
Four mitered sides per wall panel
- Calculate above
- Plinth blocks
Two per cased side when blocks replace mitered legs
- Calculate above
- Rosettes
Two per cased side at the head corners
- Calculate above
- Brad nails
Planning figure of 1.5 fasteners per foot
- Calculate above
- Caulk
One tube per 60 feet of installed trim
- Calculate above
- Filler and putty
Nail holes, corners and scarf joints
- Calculate above
Primer and finish paint are not included here. Once the trim run is known, the paint calculator converts it into cans for a trim paint estimate.
Trim guide
How this baseboard trim calculator works
Trim is bought by the running length, so the calculation starts with the perimeter of the room. The baseboard trim calculator subtracts every doorway from that perimeter, keeps the crown molding run complete because it passes over the openings, and adds casing separately for each door and window.
Each run is then divided by the stock length you can actually buy. Quantities are worked out per trim type with a cut plan: every wall run and casing leg is packed onto whole sticks, longest piece first, so an offcut is only reused when another piece actually fits it.
Take out the doorways
Doorways interrupt baseboard and chair rail but not crown. Casing is a separate order: about 17 ft of casing for one side of a standard 3 ft by 6 ft 8 in doorway, including miter waste.
Match real stock lengths
Trim is normally sold in 8, 12 and 16 ft lengths, or 2.4 to 4.8 m in metric markets. Choosing a length that covers each wall in one piece removes scarf joints and makes the finished run look cleaner.
Cut the corners correctly
Flat trim is mitered at half the corner angle: 45 degrees in a square 90 degree corner. Crown molding is different, because it leans away from the wall and needs a compound miter and bevel.
Crown molding calculator and compound miter angles
Crown molding is installed at a spring angle, the angle between the back of the molding and the wall. The two common profiles are 52/38 crown, which springs at 38 degrees, and 45/45 crown. On a flat miter saw, a 90 degree corner in 52/38 crown is cut at a 31.6 degree miter and a 33.9 degree bevel; 45/45 crown needs 35.3 degrees and 30 degrees.
Change the corner angle in the form and both settings update, which makes this a molding angle calculator for out-of-square rooms as well. Walls are rarely exactly 90 degrees, so measure the real angle with a protractor or an angle finder before cutting expensive lengths.
Many finish carpenters cope inside corners instead of mitering them, because a coped joint stays tight when the timber moves. Even then, the first cut is a miter at the calculated angle, so the numbers still apply.
Wall molding, box molding and picture molding
Decorative wall panels are ordered per panel: each box needs four mitered pieces, so a 2.5 by 3 ft panel uses 11 ft of molding before waste. Enter the number of panels and their size and the panel run is added to the order with the same waste allowance.
Picture molding, frame molding and box molding are all calculated the same way, and all four corners are cut at the flat miter angle. Keep panel spacing consistent, and set out the layout on the wall in pencil before any glue or nails.
If the panels sit below a chair rail, calculate the rail and the panels together so the whole wall arrives in one delivery and the profiles match across the batch.
Baseboard calculator for Home Depot and Lowe's stock lengths
Trim is stocked by the piece, not by the foot, so the stock length in the calculator should match what the store actually sells. Big-box stores list moulding in inches: 96 in is 8 ft, 144 in is 12 ft, and shorter 84 in and 94 in pieces turn up in some profiles. Longer 14 and 16 ft lengths are usually a special order or a lumberyard item.
8 ft · 96 in
Always in stock and fits in a car. Best for short walls, closets and casing legs, but adds a scarf joint on anything longer.
12 ft · 144 in
The usual compromise: covers most bedroom walls in one piece and still ships on a roof rack or in a pickup.
16 ft
Fewest joints on long living-room walls, but needs a trailer or delivery, and a damaged end wastes more stock.
Primed MDF is the cheapest paint-grade option and comes in the widest choice of lengths; primed finger-jointed pine costs more and handles humidity better; solid hardwood is normally ordered for stain-grade work. Pro packs of eight or more pieces are sold at a lower price per foot when a whole house is being trimmed.
Cutting reference
Miter and bevel settings
Settings for a 90 degree corner. The calculator recalculates all of them for the exact angle you measure on site.
- Baseboard and casing
- 45 degree miter, no bevel. Both pieces are cut at the same setting, in opposite directions.
- 52 / 38 crown
- 31.6 degree miter and 33.9 degree bevel when the molding is cut lying flat on the saw table.
- 45 / 45 crown
- 35.3 degree miter and 30 degree bevel. Common on smaller profiles and shallow ceilings.
- Out-of-square walls
- Measure the real corner angle first. A wall that is 3 degrees out changes the miter by 1.5 degrees.
The maths
From room perimeter to trim lengths
Every run starts from the perimeter, and the corner angles come from simple trigonometry. The spring angle is what separates a crown cut from a flat baseboard cut.
perimeter = 2 × (length + width)
baseboard = perimeter − door widths
casing = (2 × height + width + 1 ft) per cased side
flat miter = 90° − corner ÷ 2
crown miter = arctan(sin(spring) × tan(corner ÷ 2))
crown bevel = arcsin(cos(spring) × cos(corner ÷ 2))
pieces = run × waste ÷ stock length, rounded up
baseboard = perimeter − door widths
casing = (2 × height + width + 1 ft) per cased side
flat miter = 90° − corner ÷ 2
crown miter = arctan(sin(spring) × tan(corner ÷ 2))
crown bevel = arcsin(cos(spring) × cos(corner ÷ 2))
pieces = run × waste ÷ stock length, rounded up
- 01
Measure the perimeter
Room length and width, or the total run of wall for irregular rooms and hallways.
- 02
Remove the doorways
Baseboard, shoe and chair rail stop at each opening; crown molding carries on above it.
- 03
Add casing and panels
Doors, windows and decorative wall panels are counted piece by piece.
- 04
Measure the real corners
Enter the angle you measure on site; 90 degrees is the exception rather than the rule.
- 05
Buy whole lengths
Each profile is rounded up separately, because offcuts rarely serve the next wall.
Before you order
Trim and molding questions, answered
Square footage alone is not enough, because two rooms with the same area can have very different perimeters. For a rectangular room, take the square footage, choose the room proportions, and use twice the length plus twice the width. A 16 by 12 ft room is 192 sq ft and 56 ft of perimeter.
No. Each doorway interrupts the baseboard, so the width of every opening is removed from the run. Crown molding is not interrupted, because it sits above the opening.
About 17 ft for one side of a standard 3 ft by 6 ft 8 in door, which covers two legs, the head and the miter waste. Casing both sides doubles it. Every doorway is entered separately, so a 2 ft 6 in closet door and a 5 ft double door are each measured with their own size. Switch the casing detail to plinth blocks and rosettes and the legs are shortened, the head is squared off, and the blocks are counted instead.
Half the corner angle. A square 90 degree corner is cut at 45 degrees on both pieces. If the wall measures 88 degrees, each piece is cut at 46 degrees.
For 52/38 crown in a 90 degree corner, 31.6 degrees miter and 33.9 degrees bevel. For 45/45 crown, 35.3 degrees and 30 degrees. Both are recalculated for whatever corner angle you enter.
Coping is more forgiving on inside corners because the joint stays closed when the timber moves. Outside corners are always mitered, so the calculated angles are still needed.
Ten percent for straightforward rooms, and the calculator adds five more points on crown molding automatically, which matches trade practice for compound miters and coped joints. Increase to 15 or 20 percent where there are many corners, a stained finish that has to be grain matched, or a patterned profile that has to line up.
Yes. Enter the number of wall panels and their width and height, and the four mitered sides per panel are added to the order. It works the same for box, picture and frame molding.
There is nothing to install. This crown molding and baseboard calculator works in the phone browser, and adding it to the home screen from the browser menu gives it an icon like an app, which is handy when the miter saw is set up and the angles are needed on the spot.
No. It covers the trim, fasteners, caulk and filler. Once the run is known, use the paint calculator to convert the trim area into primer and finish coats.
Planning estimate only. Measure every wall and corner on site before cutting, and confirm profile sizes, stock lengths and fixing methods with your supplier. Cut angles are given for a standard compound miter saw set up with the molding flat on the table.