How to Calculate the Length of a Baseboard for a Room

Measure along the base of each section of wall in the room. Record only the areas with exposed wall at floor level. Don't include door frames and door openings in the measurements because they do not contain any walling. Record the length of each section of wall. For example, a rectangular room 15 feet long and 8 feet wide has two walls 15 feet long and two walls 8 feet long. If one of the 15-foot walls includes a door opening 3 feet wide, that wall is recorded as 12 feet long: 15 - 3 = 12.

Measure the thickness of the baseboard -- the distance it protrudes from the wall when it is held against it.

Add the thickness of the board to the length of each section of wall that terminates in an outer corner, such as where the board goes around the front of an old chimney breast. For example, if a 2 foot-long wall juts into the room, and the baseboard is 1 inch thick, record the length as 2 feet and 1 inch. The board must be longer than the wall so that it extends far enough to line up with the board placed on the adjoining wall.

Add together the lengths of all the wall sections. The result is the total length of baseboard required. For example, a room with walls measuring 15 feet 2 inches, 12 feet 2 inches and two walls measuring 8 feet 2 inches requires a total of 43 feet 8 inches of baseboard: 15 feet 2 inches + 12 feet 2 inches + 8 feet 2 inches + 8 feet 2 inches = 43 feet 8 inches. Baseboard is sold by the foot, so round up to the nearest whole foot, which would be 44 feet in this example.

Add 10 percent extra to allow for cutting errors, damaged wood and other unanticipated problems. Concluding the example, the final calculated length of baseboard would be 49 feet: 44 x 1.1 = 48.4.