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Construction & Home
Board Foot Calculator — Lumber Volume & Cost
How many board feet of hardwood or dimensional lumber you need, and what it costs
A board foot is the unit lumberyards use to price wood by volume, and a board foot calculator turns the three dimensions of a board into that number so you can buy and budget correctly. One board foot is 144 cubic inches of wood — the volume of a piece 1 inch thick, 12 inches wide and 1 foot long. It is not an area and not a linear foot, which is exactly where most people get tripped up: hardwood is sold by the board foot, trim is sold by the linear foot, and plywood is sold by the sheet, so the same plank can be quoted three different ways.
The math is simple once the units line up. With length in feet:
Board feet = (thickness in × width in × length ft) ÷ 12 × quantity.
If your length is in inches instead, divide by 144 rather than 12:
Board feet = (thickness in × width in × length in) ÷ 144.
Both formulas describe the same 144-cubic-inch unit; the only difference is whether length is measured in feet or inches. A 2×4 that is 8 ft long works out to (2 × 4 × 8) ÷ 12 = 5.33 board feet, so ten of them is 53.3 board feet. A 1×6 that is 10 ft long is (1 × 6 × 10) ÷ 12 = 5 board feet exactly.
The single biggest gotcha with dimensional softwood lumber is nominal vs. actual size. A "2×4" does not measure 2 in × 4 in — it is actually 1.5 in × 3.5 in after milling and drying. But lumber is priced and sold by the nominal size, so for buying and cost estimates you plug in the nominal numbers (2 and 4), not the actual ones. This calculator uses whatever thickness and width you type, so for store pricing enter the nominal dimensions; for an exact volume of finished material, enter the actual dimensions. Rough-sawn and 4/4–8/4 hardwood is usually quoted in quarter-inch thickness steps (4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in), and the calc rounds the total board feet up to the next whole board foot because yards don't sell fractions. Enter a price per board foot to see the material cost, and the breakdown shows the per-piece volume so you can check the math board by board.
📖 See also: How to Calculate a Tip (and Split the Bill)
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Board feet (length in feet) = (thickness in × width in × length ft) ÷ 12 × quantity • Board feet (length in inches) = (thickness in × width in × length in) ÷ 144 × quantity • One board foot = 144 cubic inches = 1 in × 12 in × 12 in • Use NOMINAL thickness and width for store pricing (a 2×4 is priced as 2 × 4) • Common hardwood thickness: 4/4 = 1 in · 5/4 = 1.25 in · 6/4 = 1.5 in · 8/4 = 2 in • Estimated cost = total board feet × price per board foot
📰 Formula
• Board feet (length in feet) = (thickness in × width in × length ft) ÷ 12 × quantity • Board feet (length in inches) = (thickness in × width in × length in) ÷ 144 × quantity • One board foot = 144 cubic inches = 1 in × 12 in × 12 in • Use NOMINAL thickness and width for store pricing (a 2×4 is priced as 2 × 4) • Common hardwood thickness: 4/4 = 1 in · 5/4 = 1.25 in · 6/4 = 1.5 in · 8/4 = 2 in • Estimated cost = total board feet × price per board foot
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Confusing board feet with linear feet or square feet — a board foot is a volume (144 cu in).
- Entering the actual size (1.5 × 3.5) when the yard prices the nominal size (2 × 4).
- Dividing by 12 when the length is in inches — use 144 for inches, 12 for feet.
- Forgetting to multiply by the quantity of boards before pricing.
- Rounding board feet down — yards charge for the next whole board foot, so round up.
💡 Tips
- For dimensional lumber pricing, always plug in the nominal thickness and width (2 and 4, not 1.5 and 3.5).
- Hardwood thickness is quoted in quarters: 4/4 = 1 in, 5/4 = 1.25 in, 6/4 = 1.5 in, 8/4 = 2 in.
- Add 15–20% extra board feet for defects, knots and cutting waste when buying rough hardwood.
- To go from board feet to linear feet, divide by (thickness × width ÷ 12) for one board size.
- Round the lot up to the next whole board foot — lumberyards don't sell a fraction of one.
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<iframe src="https://www.calcnimbus.com/embed/board-foot-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How do you calculate board feet?
Multiply thickness (in) × width (in) × length (ft), then divide by 12 and multiply by the number of boards. A 2×4 that is 8 ft long is (2 × 4 × 8) ÷ 12 = 5.33 board feet.
What is one board foot?
One board foot is 144 cubic inches of wood — the volume of a board 1 inch thick, 12 inches wide and 12 inches (1 foot) long. It measures volume, not surface area or length.
How many board feet is a 2×4×8?
Using the nominal size, (2 × 4 × 8) ÷ 12 = 5.33 board feet per 2×4 that is 8 feet long. Ten of them come to 53.3 board feet, which a yard would round up to 54.
How many board feet in a 1×6×10?
(1 × 6 × 10) ÷ 12 = 5.0 board feet. A 1×6 board ten feet long is exactly five board feet, which makes it an easy one to check the formula against.
Do I use nominal or actual size for board feet?
Use the nominal size for pricing, because lumberyards sell and price dimensional lumber by the nominal dimensions. A 2×4 is priced as 2 × 4 even though it actually measures 1.5 × 3.5 inches.
What is the difference between a board foot and a linear foot?
A linear foot measures length only; a board foot measures volume (thickness × width × length). Trim is sold by the linear foot, while hardwood is sold by the board foot, so the same plank can be quoted both ways.
How do I price lumber by the board foot?
Multiply the total board feet by the price per board foot. If you need 20 board feet of maple at $7 per board foot, the material cost is 20 × $7 = $140 before tax.
What does 4/4, 5/4 and 8/4 mean in lumber?
It is the rough thickness in quarter-inches. 4/4 is 1 inch, 5/4 is 1.25 inches, 6/4 is 1.5 inches and 8/4 is 2 inches. Enter that thickness in the calculator to get the board feet.
How do I calculate board feet when the length is in inches?
Divide by 144 instead of 12: board feet = (thickness in × width in × length in) ÷ 144. A board 2 in × 10 in × 96 in is (2 × 10 × 96) ÷ 144 = 13.33 board feet.