Lumber calculator
Work out how many stock-length boards to buy for a run of lumber, and the leftover offcut.
Lumber calculator
Work out how many stock-length boards to buy for a run of lumber, and the leftover offcut.
Enter the total length needed and the board length to see how many boards to buy.
Boards to buy
Project summary
How it works
This is a material estimate based on the stock board length you enter. It does not account for defects, crook or cutting waste unless you add your own allowance.
Lumber calculator
Why boards round up to a whole piece
Lumber yards and home centers sell boards in fixed stock lengths, most commonly 8, 10, 12 or 16 feet. If a job needs 37 feet of top plate and you are buying 8 foot boards, five boards give you 40 feet, the smallest number of full boards that covers the run. There is no way to buy 37 feet exactly, so the calculator always rounds the piece count up to the next whole board and reports the leftover as offcut.
What to do with the offcut
The offcut is not waste in the sense of material that gets thrown away. It is what is left of the last board after cutting it to fit, and on most jobs some of it gets reused for blocking, cripples or short trim pieces elsewhere in the project. If the offcut on a run comes out unusually large, it can be worth checking whether a longer stock length would use the material more efficiently, since fewer, longer boards sometimes leave less waste than more, shorter ones.
Frequently asked questions
How do I figure out how many boards I need?
Divide the total length you need by the length of the board you are buying, then round up to the next whole board, since a partial board is not something you can buy. This calculator does that division for you and also shows the offcut, the length left over once the last board is cut to fit.
Does this account for cutting waste or defects?
Not unless you set a waste percentage yourself; the default here assumes every foot of board length is usable. In practice some boards have a crook, a knot or a split end that gets cut away, so it is common to buy a bit more than the math alone suggests, especially for a run made of many short pieces where each cut adds a chance of loss.
How many 2 by 4 studs do I need for a 12 foot wall?
At 16 inch on centre spacing, you need 10 studs for a 12 foot wall. Add one for each corner and door opening. The calculator gives you the exact count based on your wall length and stud spacing.
What is the difference between a board foot and a linear foot?
A board foot is a volume measurement equal to a board 1 inch thick, 12 inches wide and 12 inches long. A linear foot is a length measurement regardless of width or thickness. The calculator handles both measurements.
How much lumber do I need for a 12 by 12 room?
A simple rectangular room needs plates, studs, headers and blocking. The calculator gives you the total based on your wall layout, stud spacing and framing members. For a 12 by 12 room, you typically need around 50 to 70 studs depending on openings.
Do I need treated lumber for a sill plate?
Yes, the sill plate must be pressure treated because it contacts the concrete foundation. The calculator can include treated lumber in the estimate if you specify it.
How much waste should I add for lumber?
A 10 to 15 percent waste factor is standard for framing lumber. More complex layouts with many angles need more. The calculator lets you set the waste percentage and shows the total with waste included.
What grade of lumber should I use for framing?
Number 2 grade is the standard for structural framing. It is strong enough for most residential applications and more affordable than higher grades. The calculator counts pieces, and you select the grade at the lumber yard.