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. 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. 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.

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.

Worked example

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.

The formula

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. 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. 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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