Board Feet Calculator
Compute the volume of a lumber board in board feet, the standard unit for pricing and ordering wood in North America. Useful for budgeting projects, comparing lumber prices, and verifying supplier invoices.
Last updated: May 2026
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About this calculator
A board foot (bf) is the standard volumetric unit for hardwood and rough-sawn lumber in North America, equal to 144 cubic inches — a piece 1 inch thick × 12 inches wide × 12 inches long. The formula used here is BF = (Length × Width × Thickness) / 144, where all three dimensions are in inches. Variables: thickness is the rough-cut or nominal thickness (hardwood lumber yards bill at nominal/quarter thickness even after surfacing), width is the rough-cut width before any straightening or jointing, and length is the rough length before final crosscut. Common hardwood thicknesses are expressed in quarters: 4/4 = 1 inch, 5/4 = 1.25 inch, 6/4 = 1.5 inch, 8/4 = 2 inch, 12/4 = 3 inch, 16/4 = 4 inch. Edge cases: dimensional softwood lumber (2×4, 2×6, etc.) is priced by piece or linear foot in most home centers; converting to board feet for cost comparison uses nominal dimensions, not actual surfaced sizes ('2×4' = 2 × 4 × length / 144 for BF math even though it's actually 1.5″ × 3.5″ after surfacing). Plywood and sheet goods are not sold in board feet; they use square footage or sheet count. Round dimensions accurately — a 5.7-inch wide board is rounded up to 6 inches for most hardwood-yard billing, which is the surcharge for partial widths. Domestic hardwoods range $4–$15/bf depending on species and grade; exotics and figured woods can exceed $40/bf; common softwoods like pine and fir are usually $1–$3/bf. The formula assumes ideal yield; real-world yield (after defects, cracks, knots, planing losses) is 70–85% of nominal volume — order 15–25% more board feet than your net finished material need.
How to use
Example 1 — single hardwood plank. Length 96 inches, width 8 inches, thickness 1.5 inches (6/4 lumber). Step 1: cubic inches = 96 × 8 × 1.5 = 1,152. Step 2: BF = 1,152 / 144 = 8 board feet. Verify: a board 1 inch thick × 12 inches wide × 12 inches long = 1 bf; this 8 bf board has 8× that volume, consistent. At $9/bf for walnut, this single board costs 8 × $9 = $72. Example 2 — bookcase project. You need: 4 shelves at 36 × 12 × 1 = 432 in³ each = 12 bf total for shelves; 2 sides at 60 × 12 × 1 = 720 in³ each = 10 bf total for sides; 1 top at 38 × 14 × 1 = 532 in³ = 3.69 bf; 1 bottom at 38 × 14 × 1 = 3.69 bf. Step 1: sum = 12 + 10 + 3.69 + 3.69 = 29.38 bf net. Step 2: add 20% waste for defects and cuts: 29.38 × 1.20 = 35.26 → round to 36 bf to order. Step 3: at $8/bf for cherry: 36 × $8 = $288. Verify: lumber yards typically bill rough-thickness, so even though your finished pieces will be 3/4 inch after planing, you pay for the 4/4 stock you bought.
Frequently asked questions
What is a board foot, and why is hardwood lumber sold in this unit instead of linear feet?
A board foot is a unit of volume equal to 144 cubic inches — the volume of a board 1 inch thick × 12 inches wide × 12 inches long. The convention dates to the late 1800s when American lumber yards needed a fair way to price wood that came in widely varying widths and thicknesses; a single-unit volume measure prevents wide hardwoods being undervalued or thin boards overvalued compared to a per-piece price. Hardwood is sold by board feet because hardwood widths and thicknesses are highly variable — a single tree yields boards from 4 to 16+ inches wide and 1 to 4+ inches thick. Softwood dimensional lumber (2×4, 2×6) has standardized sizes and is sold by linear foot or per piece because variation is minimal. Plywood and sheet goods are sold by square foot or per sheet. International conventions differ: UK and parts of Europe use Hoppus feet (a variant of board feet adjusted for log volume), Australia and New Zealand often use cubic meters, and many other countries use metric volume directly.
How do nominal lumber dimensions differ from actual dimensions, and which do I use for board feet?
Nominal lumber sizes refer to the rough-cut dimensions before drying and surfacing. Actual finished dimensions after surfacing (S2S or S4S — surfaced 2 or 4 sides) are smaller because planing removes about 0.25 inch from each surfaced face. So a '2 × 4' is actually 1.5 × 3.5 inches after planing, a '1 × 6' is 0.75 × 5.5 inches, and a '4/4' (1-inch nominal) hardwood board is typically about 0.75–0.85 inch after surfacing. For board-foot calculations: hardwood is billed at nominal/quarter thickness regardless of actual surfaced thickness — a 4/4 board is 1 inch for BF math even if it's actually 0.8 inch surfaced. Softwood dimensional lumber, when sold by board feet, is also typically billed at nominal dimensions (2 × 4 = 2 × 4 for the math). When estimating finished material yield, you must use the actual surfaced dimensions because that's what's available after planing. Many beginning woodworkers under-buy lumber because they calculate BF using actual surfaced dimensions instead of nominal — always confirm which convention your supplier uses.
What waste percentage should I add when ordering lumber for a project?
Waste percentages depend on the lumber grade, project complexity, and your skill at efficient layout. Clear, defect-free FAS-grade hardwood (Firsts and Seconds, the highest grade): add 10–15% for clean projects with straight cuts. Number 1 Common grade (the most common grade for furniture, with some defects and shorter clear sections): add 20–30%. Number 2 Common or rustic-grade (intentional knots and character): may need 35–50% waste because you cut around or accept defects. Softwood dimensional lumber for framing or simple casework: 10–15%. Projects with many small parts (drawer fronts, dovetail jigs, small turnings) generate more cutting waste than projects with long simple cuts; add 25–35% for these. Curved or sculpted parts (chair components, bent laminations) can require 40–60% waste because of grain-direction requirements. Plywood for case construction: 10–15% waste is typical. Always round up to the next available board, sheet, or pallet quantity — most suppliers don't fractionalize. A 15% over-order on $500 of lumber is $75; the alternative — running short mid-project and making a return trip — is far more costly in time and shipping.
What are common mistakes when calculating board feet?
The most common mistake is mixing units — using length in feet but width and thickness in inches in the formula, producing results 12× too small or too large. Always verify all three dimensions are in inches before applying /144. Another error is using actual surfaced thickness instead of nominal/quarter thickness, undercounting by 20–25% on hardwood orders. Calculating BF on net finished material (after waste) and ordering only that amount, instead of grossing up by 15–30% for waste, leads to running short. Forgetting that 4/4 stock is still billed at 1 inch even after surfacing to 0.85 inch is a frequent source of perceived 'overcharging' by hardwood yards. Confusing board feet with linear feet (also abbreviated 'lf') in supplier price lists — the same species can be $8/bf or $4/lf for a specific board size, and these are not directly comparable. Estimating BF for plywood or other sheet goods using the lumber formula doesn't work — plywood is sold by sheet or square foot. Finally, not adjusting for grade: a 'cheap' grade may be 30–40% off list price per board foot but produce 50% more waste, making the total project cost potentially higher than buying a higher grade.
When should I NOT use this calculator?
Skip the BF formula for plywood, MDF, particleboard, and other sheet goods — those are sold by sheet or square foot, not board feet. Do not use it for veneer, which is sold by square foot of face area regardless of thickness. Avoid it for rough log scaling at sawmills, which uses log-scale rules (Doyle, Scribner, International 1/4-inch) that account for taper and saw kerf — those produce different BF values than just measuring a single board. For dimensional softwood lumber at home centers, where pieces are priced individually, BF math is useful only for cost comparison across suppliers, not for actual purchasing. For international wood (UK, EU, Australia, NZ), local conventions use cubic meters, Hoppus feet, or other systems — not US-style BF. For finished products like flooring, decking, and lumber that's sold in pre-cut lengths, square footage or linear footage is what matters. The formula does not capture the cost of surfacing/milling labor (planing, jointing, ripping to width) — those are separate charges at hardwood yards. Finally, never use a calculated BF as your sole purchase quantity without rounding up to the next available board size, since suppliers don't typically cut to your exact spec without an upcharge.