Board Foot Calculator
Calculate board feet (BF) for any lumber project in seconds. Works with hardwood, softwood, rough or surfaced boards in inches, centimeters, feet, or meters.
Board feet (BF) is the standard volume measurement for lumber in North America, equal to a piece 12 inches wide, 12 inches long, and 1 inch thick. Builders, woodworkers, and contractors use BF to estimate hardwood and softwood lumber, calculate project costs, and verify supplier invoices.
This calculator handles the math for any thickness, width, length, and quantity, with optional inputs for waste percentage and price per board foot. The formula follows NHLA conventions for hardwoods and works just as well for dimensional softwood lumber sold by the BF. Inputs accept both imperial (inches, feet) and metric (centimeters, meters) for international users.
Board feet (BF) is the standard volume measurement for lumber in North America, equal to a piece 12 inches wide, 12 inches long, and 1 inch thick. Builders, woodworkers, and contractors use BF to estimate hardwood and softwood lumber, calculate project costs, and verify supplier invoices.
This calculator handles the math for any thickness, width, length, and quantity, with optional inputs for waste percentage and price per board foot. The formula follows NHLA conventions for hardwoods and works just as well for dimensional softwood lumber sold by the BF. Inputs accept both imperial (inches, feet) and metric (centimeters, meters) for international users.
How to Use This Calculator
Step 1: Enter board dimensions
Type the thickness, width, and length of your lumber into the three input fields. Each field has a unit dropdown on the right (inches, centimeters, feet, or meters where applicable) so you can mix units, for example, thickness in inches and length in feet.
For nominal hardwood quarter sizing (4/4, 5/4, 6/4, 8/4), enter the decimal equivalent: 4/4 is 1 inch, 5/4 is 1.25 inches, 6/4 is 1.5 inches, 8/4 is 2 inches.
Step 2: Enter quantity
The quantity field defaults to 1. If you are calculating multiple identical pieces, enter the total count. For projects with mixed sizes, calculate each size separately and add the totals.
Step 3: Read the primary result
The calculator immediately displays board feet per piece and total board feet for your quantity. These are the two numbers you will use when ordering lumber.
Step 4 (optional): Add waste percentage
Click “Show advanced options” to open the waste slider. Typical allowances:
- 10 percent for casework and shelving
- 15 percent for furniture with complex joinery
- 20 percent for veneer work or high-defect rough lumber
The calculator adjusts the total BF upward to show what you actually need to order.
Step 5 (optional): Add cost per board foot
Enter the price quoted by your lumber yard. The calculator shows total cost including the waste factor. Use the copy button to send the result to a job estimate or quote.
Reset: Click Reset in the advanced section to clear all inputs and start over with a fresh calculation.
How the Calculation Works
The standard board foot formula multiplies the lumber’s three dimensions and divides by a unit constant. Two equivalent forms exist depending on whether length is in feet or inches.
Formula (length in feet):
BF = (T × W × L) / 12
Formula (length in inches):
BF = (T × W × L) / 144
Where:
- T = Thickness in inches
- W = Width in inches
- L = Length in feet OR inches
The constant (12 or 144) converts the volume into the standard board foot unit of 144 cubic inches (one inch thick, twelve inches wide, twelve inches long).
For multiple identical pieces, multiply by quantity:
Total BF = BF per piece × Quantity
For projects with cutting waste, factor in a waste allowance:
BF with waste = Total BF × (1 + waste decimal)
For cost estimation:
Total cost = (Total BF with waste) × Price per BF
Hardwood vs softwood note: The National Hardwood Lumber Association (NHLA) measures BF using surfaced (actual) thickness and width for kiln-dried hardwoods. The Western Wood Products Association (WWPA) typically uses nominal sizes for softwoods sold as dimensional lumber. For accurate ordering, always confirm with your supplier which convention they use.
Rough vs surfaced lumber: A 1-inch rough-sawn board surfaced to 13/16 inch is still sold as 4/4 (four quarters) and the BF calculation uses the nominal 1-inch thickness. If you measure actual dimensions on surfaced lumber, you will get a lower BF count than the supplier’s invoice.
Worked Example
Scenario: Building a six-board white oak dining table top
You are planning a dining table with a top measuring approximately 72 inches long and 38 inches wide. You have decided to build it from six pieces of 5/4 (1.25 inch) thick white oak, each 8 feet long and 7 inches wide, to allow for jointing and final dimensioning.
Step 1: Calculate board feet per piece
Using the formula BF = (T × W × L) / 12:
BF per piece = (1.25 × 7 × 8) / 12 = 70 / 12 = 5.83 BF
Step 2: Calculate total board feet
Total BF = 5.83 × 6 pieces = 35 BF
Step 3: Add waste allowance
Furniture-grade joinery typically requires a 15 percent waste factor for jointing, planing, and edge cleanup.
Total with waste = 35 × 1.15 = 40.25 BF
Step 4: Calculate cost
White oak at your local yard is quoted at $8.50 per BF.
Estimated cost = 40.25 × $8.50 = $342.13
Final estimate: Order 40.25 BF of 5/4 white oak. Budget approximately $342 in lumber for the table top.
Verification tip: When the lumber arrives, the invoice should show a BF count within 2 to 3 percent of your calculation. If the supplier uses NHLA grading, they may round up to the nearest half BF per piece, which can produce a slightly higher invoice. Always check the per-piece dimensions on the invoice against what you ordered.
Understanding the Variables
Thickness (T)
The vertical dimension of the lumber, measured in inches. Hardwood thickness is sold in quarters: 4/4 (1 inch), 5/4 (1.25 inches), 6/4 (1.5 inches), 8/4 (2 inches), and so on. Softwood thickness is sold by nominal size: a 2×4 has a nominal 2-inch thickness but an actual surfaced thickness of 1.5 inches. For BF calculations, always use the nominal thickness, since that is how mills and yards price the lumber.
Width (W)
The horizontal dimension of the face of the board, measured in inches. Hardwood is sold in random widths within a grade (FAS, Select, Common), so your actual width per board may vary. For the calculation, enter the actual width if you have measured boards, or the supplier’s quoted width range if you are ordering by quantity. Softwood dimensional lumber uses nominal width: a 2×6 has a nominal 6-inch width but an actual 5.5-inch width.
Length (L)
The longest dimension of the board, typically in feet for hardwoods and softwoods sold in standard lengths (6, 8, 10, 12, 14, 16 feet). The formula uses feet as the default unit, dividing by 12. If you enter length in inches, the calculator divides by 144 instead, producing the same result.
Quantity
The number of identical pieces being calculated. For projects with multiple sizes, calculate each group separately and add the totals. Most lumber yards accept BF orders in 5 or 10 BF increments, so round up your total to ensure you have enough.
Waste Percentage
The portion of lumber that will be removed during cutting, jointing, planing, and defect avoidance. Typical waste factors by project type:
- Utility framing: 5 to 10 percent
- Casework and built-ins: 10 to 12 percent
- Furniture (modern joinery): 12 to 15 percent
- Furniture (complex traditional joinery): 15 to 20 percent
- Rough lumber with defects: 20 to 30 percent
For first-time projects in unfamiliar species, lean toward the higher end of the range.
Cost per Board Foot
The price quoted by your lumber yard, in dollars per BF. Hardwood prices range widely by species, grade, and region. Expect $4 to $7 per BF for poplar, $7 to $10 for red oak, $9 to $14 for walnut, $15 to $25 for harder exotics. Softwood dimensional lumber is typically priced per board rather than per BF, so this field is most useful for hardwood and rough specialty lumber.
Industry Standards & References
National Hardwood Lumber Association (NHLA)
The NHLA Rules for the Measurement and Inspection of Hardwood and Cypress is the definitive North American standard for measuring board feet in hardwood lumber. The current edition defines BF using surface measurement of kiln-dried, surfaced-on-two-sides (S2S) lumber, with specific rules for handling unsound wood, splits, and irregular widths. Suppliers grading to NHLA standards will reference grades like FAS (First and Seconds), Select, Number 1 Common, and Number 2 Common.
Western Wood Products Association (WWPA)
WWPA standards govern softwood lumber dimensions in North America. Western Lumber Grading Rules (WWPA Rule 17) specifies nominal versus actual dimensions for dimensional lumber such as 2x4s, 2x6s, and similar. For BF calculations on softwoods, the nominal dimension is used.
NLGA (Canadian Lumber Standards)
The National Lumber Grades Authority publishes the Standard Grading Rules for Canadian Lumber, harmonized with US standards for cross-border lumber trade. NLGA rules are equivalent to WWPA for BF measurement purposes.
ASTM D245
ASTM D245 establishes structural-grade lumber standards used in engineered construction. While not a BF measurement standard directly, projects using structural lumber may require dimensional verification against D245 specifications.
ANSI/HPVA HP-1
For hardwood plywood and veneer products, ANSI/HPVA HP-1 governs panel measurement, which uses square feet rather than board feet. If your project mixes hardwood lumber and hardwood plywood, calculate each material separately.
Industry note: Most US lumber yards selling to the trade default to NHLA grading for hardwoods and WWPA grading for softwoods. Always confirm with your supplier which standard applies, especially when ordering large volumes or specialty species. The BF measurement convention can change the final invoice by 3 to 8 percent.
Frequently Asked Questions
A board foot is the standard volume unit for lumber in North America, equal to a piece of wood 12 inches wide, 12 inches long, and 1 inch thick (144 cubic inches total). Hardwood and rough softwood lumber are typically priced and sold per board foot. The unit does not change whether the board is rough sawn or surfaced, as BF is based on nominal dimensions.
Multiply thickness (inches) by width (inches) by length (feet), then divide by 12. For example, a board that is 1 inch thick, 6 inches wide, and 8 feet long contains 4 board feet. If your length is in inches instead of feet, divide by 144. Multiply by quantity for multiple identical pieces.
Linear feet measure length only. Board feet measure volume (thickness times width times length). A 10-foot piece of 2x4 is 10 linear feet but only 6.67 board feet. For a full explanation including when to use each unit, see our complete linear feet vs board feet guide.
No. Board feet measure volume, while square feet measure area (length times width only) and ignore thickness. A 4 by 8 sheet of half-inch plywood is 32 square feet but only 16 board feet equivalent. Plywood is conventionally sold in square feet rather than BF, while solid lumber is sold in BF.
Standard waste allowances are 10 percent for casework, 15 percent for furniture, and 20 percent for projects using rough or defect-prone lumber. For first-time builds with unfamiliar species, lean toward the higher end. Experienced woodworkers running familiar processes can reduce waste to 5 to 8 percent. The waste calculation is applied to the total BF before pricing.
Use nominal dimensions for both hardwood and softwood BF calculations. A 5/4 hardwood board is calculated as 1.25 inches thick even after surfacing to roughly 1.0625 inches. A 2x6 softwood is calculated as 2 inches by 6 inches even though its actual surfaced size is 1.5 by 5.5 inches. Lumber yards price by nominal BF.
For tapered or curved pieces, treat them as the smallest rectangle that fully contains the shape. A wedge-shaped table apron cut from a board 4 inches wide at one end and 2 inches at the other is calculated as 4-inch wide stock for ordering purposes. The trim waste is included in your waste percentage allowance.
One board foot equals 144 cubic inches, and one cubic foot equals 1,728 cubic inches. Therefore, 12 board feet equals 1 cubic foot. To convert, divide BF by 12. This conversion is useful when comparing lumber volume to log volume, since logs are measured in cubic feet or Doyle/Scribner log scales.