Baseboard and skirting board calculator with corners and joints

How to calculate baseboard

You count baseboard in linear feet: the room perimeter minus the door openings, plus a cutting allowance, divided by the length of one piece and rounded up.

1. Perimeter. For a rectangular room, 2 × (length + width). If the room has bump-outs, columns or an L shape, choose "Wall by wall" and enter the walls in order as you walk around the room.
2. Doors. Baseboard stops at the door casing: take out the width of each door, measured from casing to casing.
3. Waste. We start at 10%, the figure Alexandria Moulding gives for baseboard and trim. It covers the corner cuts and a damaged piece.
4. Pieces. Length with waste ÷ piece length, rounded up. The calculator also checks a cutting plan: each run takes the full pieces that fit, and offcuts are only reused if they are long enough for another run. If the plan needs more pieces, the plan wins.
5. Joints. A wall run longer than one piece is made of two pieces or more: every extra piece is a joint.
6. Corners. A rectangular room has 4 inside corners. Every outside corner (a column against the wall, a niche, the step of an L-shaped room) brings an inside corner with it. With pre-formed corners you buy them as parts; with 45° miter cuts you need two cuts per corner.
7. Fastening. With adhesive, net length ÷ length one tube covers. With nails, one every 12 in plus one at the end of each run.

A worked example: 12 × 12 ft room

These are the values the calculator opens with in US units: a 12 × 12 ft room, one 32 in door, 8 ft pieces, 10% waste, pre-formed corners and adhesive.

• Perimeter: 2 × (12 + 12) = 48 ft
• Without the door: 48 ft - 2' 8" = 45.33 ft of baseboard
• With waste: 45.33 × 1.10 = 49.87 ft
• Pieces: 49.87 ÷ 8 = 6.23, so 7 pieces, 56 ft in all. The cutting plan gives the same count.
• Joints: three full 12 ft walls are longer than 8 ft, 3 joints. The wall with the door is two runs of 4' 8", with no joint.
• Corners: 4 inside, none outside, plus a left and a right end cap at the door
• Adhesive: 45.33 ÷ 30 = 1.51, so 2 tubes of 10 oz

With 45° miter cuts the count stays at 7 pieces and you make 8 angled cuts. With finish nails instead of adhesive, one every 12 in, you need 51 nails.

In the UK the same calculation runs in metres: a 4 × 3.5 m room with an 80 cm door and 2.4 m lengths gives 14.2 m net, 15.62 m with 10% waste, 7 lengths, 3 joints and 2 cartridges of adhesive at 10 m each.

How much baseboard for common room sizes

One 32 in door, 10% waste.

Room	Net run	8 ft pieces	16 ft pieces
10 × 10 ft	37.33 ft	6	3
12 × 12 ft	45.33 ft	7	4
12 × 14 ft	49.33 ft	8	4
14 × 16 ft	57.33 ft	8	4

The 12 × 14 ft room shows why the cutting plan matters: 54.27 ft with waste would fit in 7 pieces of 8 ft, but no 8 ft piece can hold two of the leftover runs (6 ft, 4' 8" and 4 ft), so you need 8. With 16 ft pieces none of these rooms has a joint. An L-shaped living room measured wall by wall (16, 8, 6, 4, 10 and 12 ft, one outside corner, the door on the first wall) needs 53.33 ft net, 8 pieces of 8 ft, 2 joints, 5 inside corners and 1 outside corner.

Piece lengths, corners and adhesive in the store

In the US baseboard comes mostly in 8 ft pieces, and many profiles also in 16 ft: Alexandria Moulding sells its 00608 colonial baseboard in both. Longer pieces mean fewer joints, as the table shows. In the UK skirting usually comes in lengths of about 2.4 m, like the Quick-Step flexible skirting sold by Howarth Timber.

Vinyl and many MDF skirting systems have separate accessories: inside corners, outside corners, joint connectors and left and right end caps, like the ones Leiste24 sells. The calculator counts one end cap for each side of a door. Wood baseboard is usually mitered at 45° (or coped on inside corners): choose "45° miter cuts" and the accessories drop off the list.

For adhesive in the US we start from the Liquid Nails LN-606 data sheet: a 10 oz tube gives 30 lineal feet with a 1/4 in bead, and the same sheet says to nail molding every 12 in. In metric we start from 10 m per cartridge, the low end of the 10-12 m stated for Soudal 50A in a 310 ml cartridge. On wavy walls the adhesive runs out sooner: change the coverage in the advanced options.

Common mistakes

• Dividing the total by the piece length and stopping there. Four walls of 4' 3" with 8 ft pieces come to about 18.7 ft with waste, which looks like 3 pieces, but each piece only gives one 4' 3" run: you need 4.
• Forgetting doors between two rooms. If you calculate two rooms together, the door that joins them breaks the baseboard on both sides: count it in both rows.
• Miscounting the corners of a column. A column against the wall adds 2 outside and 2 inside corners and makes the perimeter longer by twice its depth: measure that room wall by wall. A freestanding column has 4 outside corners and no inside ones: add its 4 sides as walls and count 4 outside corners.
• Mixing pieces from different lots. Wood color and factory finish change from one lot to the next: buy all the pieces at once, with a spare if the room has a lot of corners.