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Whether you’re building a deck, putting up a fence, or framing a new structure, using our board feet calculator will quickly determine how much lumber to buy before you head to the store, saving time, money, and a second trip. Enter your board dimensions, quantity, and a waste factor below and we’ll calculate your total board feet, adjusted for waste, and give you an estimated cost.
Board Feet Calculator
🪵 Board Feet Calculator
Calculate lumber for decks, fences, and framing projects
Estimates only. Always confirm with your lumber supplier before purchasing.
What Is a Board Foot?
A board foot is a unit of lumber volume equal to a piece of wood 1 inch thick, 12 inches wide, and 12 inches long — or 144 cubic inches in any other combination. It’s the standard unit lumber yards use to price and sell wood, so knowing your board feet is the starting point for any lumber estimate. NC State Extension defines a board foot as 144 cubic inches of wood, the same as a board 1 inch thick, 12 inches wide, and 1 foot long.
How to Calculate Board Feet
The formula is straightforward: multiply the thickness (in inches) × width (in inches) × length (in feet), then divide by 12. For example, a 2×6 board that’s 10 feet long works out to (2 × 6 × 10) ÷ 12 = 10 board feet. The calculator above handles all of this automatically — just enter your dimensions and quantity.
How to Calculate Board Feet by Hand
A board foot is a piece of wood 1 inch thick, 12 inches wide, and 12 inches long, or 144 cubic inches. To find board feet by hand, multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. For example, one 2×6 that’s 8 feet long is 2 × 6 × 8 ÷ 12 = 8 board feet. Ten of them is 80 board feet.
Most lumberyards figure board feet using nominal sizes, so a 2×6 counts as 2 inches by 6 inches even though it actually measures 1.5 by 5.5. The math is simple for one board, but it adds up fast on a deck or fence with dozens of boards in different sizes. That’s what this board feet calculator is for: enter each size once and it totals the whole project, adds your waste factor, and estimates the cost.
How Much Waste Should I Add?
Always add a waste factor to your lumber estimate. For a straightforward deck or fence with standard cuts, 10% is typical. If your project involves angled cuts, a herringbone pattern, or a lot of notching, bump it to 15–20%. Running short on lumber mid-project is far more frustrating than having a few extra boards left over.
Board Feet vs. Linear Feet — What’s the Difference?
Linear feet measures length only — useful for things like trim, molding, or fence rails where thickness and width are fixed. Board feet measures volume, which accounts for thickness and width too. When buying dimensional lumber like 2×4s or 2×6s for a deck or fence, board feet gives you the complete picture of how much material you actually need.
Tips for Buying Lumber for Deck and Fence Projects
Buy all your lumber from the same lot at the same time if possible — wood color and grain can vary between batches, and mismatched boards are obvious once stained. Let pressure-treated lumber dry for at least 2–3 weeks before staining or sealing, otherwise the finish won’t penetrate properly. And always apply a wood conditioner before staining — it helps the stain absorb evenly, especially on softer woods like pine. Building a fence? Use our fence calculator to figure out how many posts, rails, and pickets you need before you price out the lumber.
Frequently Asked Questions About Using a Board Feet Calculator
How many board feet are in a 2x4x8?
A 2×4 that’s 8 feet long is 2 × 4 × 8 ÷ 12 = 5.33 board feet.
Why should I add a waste factor?
Some boards will have knots, splits, or warping, and every project has cuts that leave short pieces you can’t use. Adding 10 to 15 percent to your total covers that waste, so you don’t have to make a second trip to the store halfway through the job.
Is a board feet calculator only for hardwood?
No. Board feet are used for all kinds of lumber. Hardwood is almost always sold by the board foot, and the same math helps you compare prices and plan any deck, fence, or framing project, even when the store sells the boards by the piece.