Lumber Calculator
Calculate board feet and total cost for your lumber needs. Add multiple line items for a full materials list.
Lumber Dimensions
Board Feet (per piece)
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Total Board Feet
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Total Cost
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Common Lumber Sizes
| Nominal | Actual | BF per 8ft | Common Use |
|---|---|---|---|
| 2x4 | 1.5" x 3.5" | 5.33 | Framing, studs |
| 2x6 | 1.5" x 5.5" | 8.0 | Floor joists, decking |
| 2x8 | 1.5" x 7.25" | 10.67 | Headers, rafters |
| 2x10 | 1.5" x 9.25" | 13.33 | Floor joists, beams |
| 2x12 | 1.5" x 11.25" | 16.0 | Ridge boards, stairs |
| 4x4 | 3.5" x 3.5" | 10.67 | Posts, columns |
Board Feet Formula
Board Feet = (Thickness in inches x Width in inches x Length in feet) / 12
One board foot = a piece of lumber 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches).
Adds your lumber takeoff into the Construction Estimate Builder.
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Frequently Asked Questions
What is a board foot and how is it calculated?
A board foot (BF) is the standard unit of measure for hardwood lumber. It equals a piece of wood 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches). The formula is: Board Feet = (Thickness in inches x Width in inches x Length in feet) / 12. Lumber yards price hardwoods by the board foot, while dimensional softwood (2x4s, etc.) is typically priced per linear foot or per piece.
What is the difference between nominal and actual lumber sizes?
A "2x4" does not actually measure 2 inches by 4 inches. After drying and planing, its actual dimensions are 1.5" x 3.5". This applies to all dimensional lumber: a 2x6 is actually 1.5" x 5.5", a 2x8 is 1.5" x 7.25", and so on. When calculating board feet for purchasing, use nominal dimensions if your supplier prices by nominal, or actual dimensions for precise volume calculations.
How much extra lumber should I buy for waste?
A good rule of thumb is to add 10-15% extra for waste, depending on the project. Simple framing with few cuts may only need 10%. Projects with many angled cuts (like stairs or rafters) should budget 15-20%. Hardwood projects should also account for boards you may reject due to knots, warping, or defects -- add 15-20% for hardwoods.
Worked Example: Deck Framing Lumber
Project: 12x16 ft deck requiring 14 joists of 2x8x12 at $4.00 per board foot
Step 1 - Board feet per piece: (2 x 8 x 12) / 12 = 16 BF per joist
Step 2 - Total board feet: 16 x 14 = 224 BF
Step 3 - Total cost: 224 x $4.00 = $896.00
Step 4 - Add 10% waste: $896 x 1.10 = $985.60 (buy 15-16 joists to be safe)
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