How to use
- Measure the inside length and width of the room at the floor.
- Count doorways where baseboard will not run. A cased opening counts if you will stop the trim there. Enter the clear width you will skip, often about 3 feet for a passage door.
- Add any other gap, such as a fireplace opening, as a single total in feet.
- Press Calculate. If you know the price of a foot of the molding you chose, enter it for a material total. Reset restores the door defaults.
How it's calculated
Linear feet = perimeter − (doors × door width) − other openings
Each corner is already included when you walk the perimeter. Buying an extra stick for a bad cut is a separate decision; this formula does not hide a waste percent, because trim waste depends on the stick length at the store. If sticks are 16 feet, divide the linear feet by 16 and round up, then decide whether the offcuts can start the next wall.
Shoe molding and door casing are different profiles. Door casing goes around the opening you just subtracted, so do not reuse this length for casing. Floor area for the same room is on the square footage calculator.
Worked example
A 12 by 10 foot room has a perimeter of 2 × (12 + 10) = 44 feet. One 3 foot door removes 3 feet, leaving 41 linear feet of baseboard. At $2.15 per foot the material is 41 × 2.15 = $88.15, before waste from cutting 16 foot sticks and before paint.
Assumptions and sources
The perimeter formula is the definition of a rectangle’s boundary. It assumes the room is rectangular. For an L-shape, split the outline into rectangles or measure the walls with a tape and type the total as if it were a rectangle whose perimeter matches, by setting length and width so that 2 × (length + width) equals that tape total and setting openings separately. Inside corners and outside corners do not add length.
FAQ
Do corners mean I need more baseboard?
No. A corner is where two pieces meet. The total length is still the perimeter. You may need an extra stick because a cut rarely lands exactly on a corner.
What door width should I use?
Use the width of the gap where baseboard will not be installed. A common passage door is about 3 feet of clear opening, but measure yours. The 3 in the form is only a starting value.
Should I include closet doors?
Skip the opening only if baseboard stops at the closet door. If you run baseboard inside the closet, measure the closet as its own room.
How is this different from square footage?
Square footage multiplies length by width and answers how much floor you have. Baseboard adds length and width, doubles that sum, and answers how much trim you have.