Board Feet to Square Feet Conversion

The conversion formula

A board foot is a volume: 144 cubic inches. A square foot is an area. To go from volume to area, you divide out the thickness:

Square feet = board feet / thickness (inches)

Going the other direction is just as easy:

Board feet = square feet x thickness (inches)

Both formulas use the nominal thickness, the same nominal sizes you use for board feet in the first place.

Why thickness decides everything

One board foot of 1-inch lumber covers exactly 1 square foot of face, because 1 board foot is 144 cubic inches and a 1-inch-thick layer of 1 square foot is also 144 cubic inches. Double the thickness and the same volume covers half the area. That gives the memorable rule: for 1-inch (4/4) stock, board feet and square feet are equal. For 2-inch (8/4) stock, square feet are half the board feet. For 3/4-inch stock, square feet are board feet divided by 0.75, which is a third more coverage per board foot.

Worked example 1: 600 board feet of 2-inch stock

Square feet = 600 / 2 = 300 square feet. This is the number you need when a project calls for 2x decking and you are comparing a per-board-foot quote against a per-square-foot price.

Worked example 2: flooring from 1-inch stock

You need 450 square feet of 3/4-inch hardwood flooring. Board feet = 450 x 0.75 = 337.5 board feet. Flooring is almost always quoted by the square foot, so run this direction when the yard gives you a per-board-foot price and you want to know what the floor actually costs. Note this is the net coverage; flooring tongue-and-groove waste and end matching mean you should buy 10 percent more, about 371 board feet here.

Worked example 3: a deck in 2x6

A 16 by 20 foot deck is 320 square feet of surface. If the decking is nominal 2-inch material, the board footage for the surface alone is 320 x 2 = 640 board feet. Framing joists, beams, and rim boards add more on top, and 5/4 decking (1.25 inches nominal) is common too: 320 x 1.25 = 400 board feet for the surface. Always confirm which nominal thickness your decking actually is before converting.

Conversion table

• 100 board feet of 1 in stock = 100 sq ft
• 100 board feet of 1.25 in (5/4) stock = 80 sq ft
• 100 board feet of 1.5 in stock = 66.7 sq ft
• 100 board feet of 2 in stock = 50 sq ft
• 100 board feet of 3 in stock = 33.3 sq ft
• 100 board feet of 4 in stock = 25 sq ft

When you do not need this conversion at all

If both sides of a quote are already in the same unit, skip converting. Sheet goods like plywood and OSB are sold by the sheet and planned by the square foot, so no board-foot math is involved. Dimensional softwood at the home center is sold by the piece with the price on the tag, so converting to board feet only matters when you are comparing against a hardwood yard quote. The conversion earns its keep in exactly one situation: one side of the deal is priced per board foot and the other side is planned in square feet.

Common mistakes

Using actual thickness. The formulas run on nominal thickness, matching how board feet are priced. A nominal 2x board counts as 2 inches here even though it measures 1.5 inches.

Converting 5/4 decking as 1 inch. 5/4 stock is 1.25 inches nominal, so 320 square feet of it is 400 board feet, not 320. That 25 percent error is an entire delivery truck on a big deck.

Forgetting that flooring coverage is net. The square footage of flooring you buy is gross; tongue-and-groove, end joints, and rip cuts reduce installed coverage. Add 10 percent for straight rooms, 15 percent for rooms with lots of angles.

Mixing board feet with linear feet. Linear feet measure length only and ignore width and thickness entirely. A 2x4 and a 2x12 both cost different amounts per linear foot because their board footage per foot differs. See our guide on how to calculate board feet for the per-foot numbers.