How to use this calculator
- Choose trim type. Select baseboard, crown molding, chair rail or door/window casing.
- Enter field dimensions. Use room length and width for perimeter trim, or opening width and height for casing.
- Set stock and waste. Enter the purchased stock length, waste allowance and optional price per stock piece.
- Buy whole pieces. Use the rounded stock-piece count, then build a separate cut list for exact joints and offcuts.
How it works
Perimeter trim starts from the measured room perimeter. Baseboard and chair rail subtract doorway or opening widths; crown molding keeps the ceiling-line perimeter.
perimeter = 2 x (room_length + room_width) x room_count
net_trim = perimeter - opening_count x opening_width
trim_with_waste = net_trim x (1 + waste / 100)
stock_pieces = ceil(trim_with_waste / stock_length)
Door and window casing mode uses a three-piece assumption per opening:
casing_length = opening_count x (2 x opening_height + opening_width)
Worked example
Verified against the live calculator
A 12 ft x 10 ft room has a 44 ft perimeter.
With two 3 ft door openings, baseboard net length is
38 ft. With 10% waste, the needed length is
41.8 ft, so 12 ft stock rounds up to
4 pieces.
Frequently asked questions
How do you calculate baseboard linear feet?
Start with room perimeter, 2 x (length + width), multiply by the number of identical rooms, subtract doorway or opening widths, then add a waste allowance and round up to whole stock lengths.
Should crown molding subtract door openings?
Usually no. Crown runs at the ceiling line, so the calculator keeps the full room perimeter for crown molding. Baseboard and chair rail modes subtract average opening width.
How does casing mode work?
Casing mode estimates three-piece casing: two vertical legs plus one head piece per opening. It is a material takeoff, not a detailed cut plan.
How much trim waste should I allow?
Ten percent is a common screen for simple rooms. More corners, scarf joints, stain-grade matching, bowed stock or complex casing layouts can need a larger allowance.
Method & assumptions
- This is a quick material takeoff, not a cut optimizer.
- Baseboard and chair rail subtract average opening width; crown molding does not.
- Casing mode assumes two side legs and one head piece per opening. Add sill, apron or four-sided picture-frame casing separately if needed.
- Waste covers miters, scarf joints, defects and attic stock, but exact offcut reuse depends on the final cut sequence.
- For adjacent finish-carpentry planning, use the compound miter, cut list, wood stain coverage and board feet calculators.