A board foot calculator works the unit hardwood and rough lumber are sold by: a board foot is a piece one inch thick, twelve inches wide and one foot long, 144 cubic inches, and every other piece is a multiple of it. The board feet calculator is thickness in inches times width in inches times length in feet, divided by 12; or all three in inches, divided by 144. The trap is nominal against actual size, because a 2x6 is sold as 2 by 6 and measures less, and lumber is priced by the nominal board foot. This page states the formula, works it on framing and finish stock, says which size to use, and shows how the board footage calculator prices the order; the free construction cost estimator on this site carries the lumber line into the estimate, with no account.
The board feet formula, two ways
Board feet equals thickness in inches times width in inches times length in feet, divided by 12. A 2x6 twelve feet long is 2 times 6 times 12 divided by 12, 12 board feet. A 2x10 sixteen feet long is 2 times 10 times 16 divided by 12, 26.7 board feet. A 1x8 ten feet long is 1 times 8 times 10 divided by 12, 6.67 board feet. With all three dimensions in inches the divisor is 144: a 2x6 at 144 inches is 2 times 6 times 144 divided by 144, 12, the same answer. A board foot calculator is that multiplication, and a whole order is the sum over the pieces, which is why the count of pieces by size comes first.
Nominal or actual: which size the board footage calculator uses
Dimension lumber is sold by its nominal size and priced by the nominal board foot, so a 2x6 is worked as 2 by 6 even though the dressed piece measures less; hardwood sold rough is measured by its actual thickness and width, in quarters of an inch for thickness, and the calculator uses those. Use the size the seller prices by, and for a mixed order say which on each line. The National Institute of Standards and Technology's Handbook 44 is where the measuring rules themselves are published, and the American Wood Council covers the grades and sizes the stock is specified in.
A framing package worked in board feet
Take the 24-foot 2x6 exterior wall from the framing calculator: 19 studs in the run plus about 30 pieces at corners and openings, 49 studs at 8 feet, and 72 feet of 2x6 plate in 12-foot pieces. The studs are 49 times 2 times 6 times 8 divided by 12, 392 board feet; the plates are 6 pieces times 2 times 6 times 12 divided by 12, 72 board feet; the headers, say two doubled 2x10s at 4 feet, are 4 times 2 times 10 times 4 divided by 12, 26.7 board feet. The wall is about 491 board feet of stock before cut waste, which at the yard's price per board foot is the lumber line, and at the yard's price per piece is the same line by another route.
From board feet to the order and the estimate
The order is by piece and length, because that is what the yard stocks; the board feet are how the price is checked and how a hardwood or rough-sawn line is bought. Either way the lumber line is the count times the price plus the contractor's cut waste, marked up at the contractor's overhead and profit into the estimate. The free construction cost estimator on this site carries the framing and finish lumber at the contractor's own cost per square foot with site work, contingency and overhead and profit shown, and the schedule of values carries the same lines as work in place when the framing is billed.
Questions people ask about board foot calculator
What is the board foot formula?
Thickness in inches times width in inches times length in feet, divided by 12; or all three in inches divided by 144. A 2x6 twelve feet long is 12 board feet.
Do I use nominal or actual size in a board feet calculator?
The size the seller prices by: nominal for dimension lumber (a 2x6 is worked as 2 by 6), actual for rough hardwood measured in quarters. Say which on each line of a mixed order.
How many board feet in a framed wall?
Sum the pieces: on a 24-foot 2x6 wall with two windows, about 392 board feet of studs, 72 of plates and 27 of headers, around 491 before cut waste.