Baseboard calculator
This measures the run of trim around a plain rectangular room and cuts it into stock lengths. A room with bays, returns or an open plan will differ, and coped inside corners eat a little extra, so walk the walls with the number before you buy.
Enter the room size, the width of the doorways where trim stops, and the length of the sticks you can buy. The tool totals the perimeter, takes out the openings, adds a waste margin and counts the pieces.
Exemple détaillé
A 12 ft × 10 ft room has a perimeter of 2 × (12 + 10) = 44 feet. Deduct two 3-foot doorways and you have 38 feet of trim to run. Add 10% for mitres and it is about 42 feet; in 8-foot sticks that is 42 ÷ 8 = 5.25, so 6 pieces.
In metric: a 3.6 m × 3 m room is 2 × (3.6 + 3) = 13.2 m around. Take off two 0.9 m doorways for 11.4 m; with 10% it is 12.54 m, and in 2.4 m lengths that is 12.54 ÷ 2.4 = 5.2, so 6 pieces.
Sur le chantier
Pick the stock off the longest wall. That 38 ft of trim with 10% is 41.8 ft. In 8-footers it is 6 sticks, in 12s it is 4 and in 16s it is 3 — all 48 ft, so the price is close. The difference is joints: the 12 ft wall in 8 ft stock has a scarf in the middle of it, in 12 ft stock it is one piece, and in 16 ft stock the offcut runs the next wall. Buy the length that clears your longest wall and let the short walls eat the offcuts.
The closet counts. A 12 × 10 bedroom with a 6 × 2 closet: the room is 44 ft less the 3 ft door and the 5 ft closet opening = 36 ft, and the closet inside is 2 × (6 + 2) = 16 ft less its own 5 ft opening = 11 ft. Forty-seven feet, not thirty-eight. Put the closet in as its own room and add the two.
A whole floor, one order. Three bedrooms at 44 ft, a hall at 48 ft, a living room at 64 ft, less nine doorways at 3 ft: 244 − 27 = 217 ft, × 1.1 = 239 ft, in 16 ft stock 15 pieces. Shoe or quarter-round is the same length again on its own line. (In metric: 217 ft is about 66.1 m, × 1.1 = 72.8 m, and in 4.8 m stock that is 16 pieces.)
What went wrong?
Quick referencefor trim
- Perimeter
- 2 × (length + width)
- Openings
- a door about 3 ft (0.9 m) · a closet opening 4–6 ft (1.2–1.8 m) · a cased opening as measured
- A 12 × 12 room, one door
- 45 ft · with 10%: 50 ft → 7 eights, 5 twelves, 4 sixteens
- A 3.6 × 3.6 m room, one 0.9 m door
- 13.5 m · with 10%: 14.9 m → 7 × 2.4 m, 5 × 3.6 m, 4 × 4.8 m
- Sticks
- linear feet ÷ stock length, rounded up
- Shoe / quarter-round
- the same linear feet again
- Métrique
- 1 m = 3.28 ft · 2.4 m stock ≈ 8 ft · 3.6 m ≈ 12 ft
Waste & overagewhat to add, and why
- Trim carpenters add about 10% on a square room and closer to 15% where every wall has an inside and an outside corner — every mitre wastes the cut-off, and coping an inside corner burns an inch or two per joint. The waste field starts at 10%.
- Buy stock in the longest length the room's longest wall needs, so a 14 ft wall is one piece: a joint in the middle of a wall costs more time than the extra foot of moulding.
- Keep one full stick beyond the count as a spare — a split nail hole on the last piece otherwise means a second trip for one length.
Mistakes to catchbefore you order
- Deducting the doorway but forgetting the closet and the pass-through; every opening where the base stops comes off, and the tool's one openings field wants their total width.
- Adding the perimeter of an L-shaped room as if it were the rectangle around it; walk the actual walls with the tape and type the true perimeter as the length with width 0.
- Ordering by linear feet and then buying 8 ft sticks without checking the count — the sticks line depends on the stock length field, so set it to what the yard actually sells.
La formule
linear = (2 × (L + W) − openings) × (1 + waste) · pieces = linear ÷ stock, rounded up
The perimeter is twice the sum of the two room dimensions. Subtract the doorways where the base actually stops, add the waste margin for coped corners and mis-cuts, then divide by the length of one stick and round up to whole pieces.
Questions
- How do I work out how much baseboard I need?
- Add up the wall lengths around the room — that is the perimeter — subtract the door openings, and add a little for mitre cuts and mistakes. A 12 by 10 foot room has a 44-foot perimeter; take out two 3-foot doorways and you are trimming 38 feet, or around 42 with waste. In metric, a 3.6 by 3 m room is 13.2 m around, 11.4 m less two 0.9 m doorways. This tool does the perimeter and the deductions for you.
- How many lengths of trim is that?
- Divide the linear footage by the stock length you can buy and round up. Forty-two feet of trim in 8-foot sticks is 42 ÷ 8 = 5.25, so six pieces; in metric, 12.5 m in 2.4 m lengths is 5.2, so six. Longer sticks mean fewer joins on a long wall, but they are harder to carry home and to handle around corners — pick the length that suits the room.
- Do I subtract every doorway?
- Subtract the cased openings where trim genuinely stops — doorways, a hearth, a wide passage. Do not bother deducting a single door slab or a window, since base runs under a window anyway and the offcuts rarely save you a stick. Enter the total width of the true openings and leave the rest in.
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