Lumber & framing · free tool
Board Foot Calculator
Find the board feet and cost of your lumber. Add each board, pick the thickness in quarters or a nominal size, and get total BF plus price.
Board Foot Calculator
Board feet & cost of your lumber — board by board.
1 Your boards
2 Board footage
| Board | Size | BF |
|---|
Estimates only — hardwood is priced on nominal size even after surfacing; add a little for defects and cuts. See how we calculate · Updated monthly
Method · how it works
How to calculate board feet
A board foot is a volume: 1 inch thick by 1 foot square, or 144 cubic inches. Here is exactly what the calculator does, so you can check it by hand.
Measure the board
Thickness and width in inches, length in feet. Hardwood thickness is often given in quarters (4/4 = 1 in).
Multiply the three
Multiply thickness × width × length together to get the raw volume.
Divide by 12
Divide by 12 for board feet (or by 144 if your length is in inches too).
Pieces & price
Multiply by how many boards, then by the price per board foot for cost.
A 4/4 × 6 in × 8 ft board
1 × 6 × 8 = 48
48 ÷ 12 = 4 board feet
one 1x6x8 hardwood board
Sources: board-foot definition (144 cu in / FBM) · Woodworkers Source · hardwood-grade references
Verified against standard board-foot charts · Updated monthly
Estimates only. Lumber yards price hardwood on nominal size even after it's surfaced — and always buy a little extra for defects, snipe and cutting waste.
Board feet · by size
Board feet by board size
Board feet at 8 ft long, using nominal sizes. Pick your board in the calculator above for any length and quantity.
The framing standard — 2 × 4 × 8 ÷ 12.
FramingJoists, plates and heavier framing.
FramingFloor and ceiling joists.
FramingBeams, headers and stair stringers.
FramingOne-inch (4/4) hardwood board.
HardwoodTwo-inch (8/4) stock for legs and thick tops.
HardwoodSame rule every time: thickness × width × length ÷ 12 — longer boards and thicker stock give more board feet.
Sizing · what's real
Nominal vs actual lumber size
The size on the label isn't the size you get. A "2x4" is really 1½ x 3½ inches — but board feet are figured on the nominal size.
Softwood: nominal vs actual
| Nominal | Actual (in) |
|---|---|
| 2x4 | 1.5 x 3.5 |
| 2x6 | 1.5 x 5.5 |
| 2x8 | 1.5 x 7.25 |
| 2x10 | 1.5 x 9.25 |
| 1x6 | 0.75 x 5.5 |
| 4x4 | 3.5 x 3.5 |
Hardwood is sold in quarters
Thickness in 1/4-inch steps
You still pay for the nominal size. A 4/4 board planed down to 3/4 in is billed as a full 1-inch board foot — you're paying for the rough lumber the mill dried and surfaced.
Know the difference
Board feet vs linear feet vs square feet
Three ways lumber and materials get measured — each answers a different question, and each is priced differently.
The volume of the wood — thickness, width and length. How hardwood and rough lumber is priced, because thicker and wider boards contain more wood.
Just the length, ignoring width and thickness. How dimensional lumber, trim and moulding are often sold — a "2x4x8" is 8 linear feet.
The area a material covers. How flooring, plywood and decking coverage are measured. Find it with the square footage calculator.
Rule of thumb: buy hardwood by the board foot, framing and trim by the linear foot, and sheet goods and coverage by the square foot.
Buying lumber
How lumber is priced by the board foot
Hardwood dealers and sawmills quote a price per board foot. What you pay per BF depends on the species, grade and how the wood is surfaced.
Species & grade
Price climbs with rarity and clarity. Framing pine runs low; walnut and exotics run high. FAS is the top grade; #1 and #2 Common have more knots and cost less.
Rough vs surfaced
Rough lumber is cheapest but needs planing. S2S is surfaced two sides, S4S all four — more finished, more per board foot, less work for you.
Add for waste
Order 15–30% extra board feet for defects, snipe, checks and cutting around knots — more for short parts or figured wood you'll cull heavily.
Enter your rate
Put your yard's price per board foot in the calculator's Cost tab to total a whole cut list. Get a current quote — lumber prices move with the market.
As a rough guide, framing softwood often falls near $0.80–1.50 per board foot while hardwoods vary widely by species and grade — always confirm today's price with your supplier before ordering.
Answers
Board foot FAQs
What is a board foot?
A board foot is a unit of lumber volume equal to 144 cubic inches — a board 1 inch thick, 12 inches wide and 1 foot long. It's abbreviated BF, bd ft or FBM.
How do I calculate board feet?
Multiply thickness (in) x width (in) x length (ft), then divide by 12. If the length is in inches too, divide by 144 instead.
How many board feet are in a 2x4x8?
A 2 x 4 x 8 ft is 5.33 board feet — 2 x 4 x 8 ÷ 12. A 2x6x8 is 8 BF and a 2x8x8 is 10.67 BF.
What does 4/4 mean in lumber?
Hardwood thickness is measured in quarter-inches. 4/4 = 1 inch, 5/4 = 1.25, 6/4 = 1.5, and 8/4 = 2 inches — even after the board is surfaced thinner.
What is the difference between board feet and linear feet?
Linear feet measure length only; board feet measure volume (thickness x width x length). Hardwood sells by the board foot, trim by the linear foot.
Why is hardwood sold by the board foot?
Because it accounts for thickness and width, not just length — a wider or thicker board holds more wood, so board feet give a fair, consistent price.
How much extra lumber should I buy?
Add 15–30% in board feet for defects, cutting waste and cull — more for short parts, figured wood or lower grades with more knots.
Do I use nominal or actual size for board feet?
Use nominal size — the way lumber is sold and priced. A 4/4 board surfaced to 3/4 in is still billed at the full 1-inch board foot.