Whether you're sourcing hardwood for a dining table, pricing out deck boards, or estimating how much lumber a sawmill run will yield, this board feet calculator does the heavy lifting for you. Enter your dimensions and price per board foot, and you'll instantly know the total board footage and exactly what you'll spend — no pen, paper, or mental math required.
The calculator accepts thickness, width, and length in any unit — inches, feet, meters, millimeters, or centimeters — so it works whether you're shopping at a local hardwood dealer in imperial measurements or sourcing materials internationally in metric. Add the number of pieces and your price per board foot, and you've got a complete lumber cost estimate in seconds.
What Is a Board Foot?
A board foot is the standard unit of measurement for lumber volume in the United States and Canada. One board foot equals a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long — or any combination of dimensions that produces the same volume (144 cubic inches).
Lumber yards and hardwood dealers price wood by the board foot rather than by the piece because boards come in wildly varying sizes. A 4-inch-wide plank and a 10-inch-wide plank of the same length contain very different amounts of wood — board feet captures that difference. Once you understand this, price tags at the lumber yard start to make a lot more sense.
Board feet measure volume, not area. This is why a thicker board costs more even when the surface dimensions look the same.
The Board Feet Formula
The calculation itself is straightforward once you know the formula:
Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12
Or equivalently, if all dimensions are in inches:
Board Feet = (Thickness × Width × Length) ÷ 144
For multiple pieces, multiply the result by the number of boards:
Total Board Feet = Board Feet per piece × Number of pieces
Worked Example: You need 6 pieces of oak that are 1.5 inches thick, 8 inches wide, and 8 feet long.
- Board feet per piece = (1.5 × 8 × 8) ÷ 12 = 8 board feet
- Total board feet = 8 × 6 = 48 board feet
- At $12 per board foot: Total cost = $576
This calculator handles all of that in a single step — just fill in the fields and the totals appear instantly.
How to Use This Calculator
Step 1 — Enter the number of pieces Type in how many individual boards you're working with. If you're calculating a single plank, enter 1. For a full lumber order, enter the total piece count.
Step 2 — Enter the thickness Type your board's thickness and select the matching unit from the dropdown (inches, feet, meters, millimeters, or centimeters). Most dimensional lumber in the US is measured in inches — a "2x4" is nominally 2 inches thick (actually 1.5 inches finished).
Step 3 — Enter the width Same process — enter the width value and choose your unit. Keep in mind that lumber sold as "nominal" sizes (like 2x6, 1x8) is slightly smaller after milling. Use the actual measured width for the most accurate board footage.
Step 4 — Enter the length Enter the board length with its unit. Lengths are often stated in feet at the lumber yard (6', 8', 10', 12'), but you can enter in any unit the calculator supports.
Step 5 — Enter the price per board foot Check your supplier's current pricing and enter the cost per board foot. This varies significantly by species — construction pine might run $2–4/bf while figured walnut or exotic hardwoods can exceed $20–30/bf.
Step 6 — Read your results Total Board Feet and Total Cost update automatically. No need to click calculate.
Common Lumber Sizes Reference
Lumber in the US is sold by nominal dimensions, but the actual (dressed) sizes are smaller. Here's a quick reference:
Nominal Size | Actual Size | Board Feet per 8' Length |
|---|---|---|
1×4 | 0.75" × 3.5" | 1.75 bf |
1×6 | 0.75" × 5.5" | 2.75 bf |
1×8 | 0.75" × 7.25" | 3.63 bf |
1×12 | 0.75" × 11.25" | 5.63 bf |
2×4 | 1.5" × 3.5" | 3.5 bf |
2×6 | 1.5" × 5.5" | 5.5 bf |
2×8 | 1.5" × 7.25" | 7.25 bf |
2×12 | 1.5" × 11.25" | 11.25 bf |
Tip: Hardwood dealers typically sell rough-sawn lumber at full nominal dimensions (so a 4/4 board really is 1 inch thick), while construction lumber from big-box stores is sold at finished/dressed sizes.
Calculating Lumber Cost
The cost field in this calculator uses a simple formula:
Total Cost = Total Board Feet × Price per Board Foot
Lumber pricing varies widely by:
- Species — Common pine and SPF (spruce-pine-fir) construction lumber is inexpensive at $2–5/bf. Popular hardwoods like maple, oak, and cherry run $6–15/bf. Premium or figured hardwoods (tiger maple, crotch walnut, live-edge slabs) can be $25–50/bf or more.
- Grade — Clear, knot-free lumber commands a premium. #2 common grade with knots is substantially cheaper.
- Thickness — Thicker stock (8/4, 12/4) often costs more per board foot than standard 4/4 lumber due to limited supply and longer drying time.
- Market conditions — Lumber prices fluctuate with housing demand, trade policy, and seasonal availability. Always confirm current pricing with your supplier before budgeting a project.
For larger projects, getting a few board-foot quotes from different suppliers before committing can save a meaningful amount.
Using Metric Measurements
Most board-foot calculators online only accept inches and feet — which is a real limitation if you're working from metric plans or sourcing internationally. This calculator accepts meters, centimeters, and millimeters alongside the standard imperial units for every dimension.
Simply enter your thickness, width, and length in whichever unit you have on hand and select the matching unit from the dropdown. The calculator converts everything internally and outputs your result in board feet — the unit your lumber supplier will quote regardless of where the wood originated.
Tips for Buying Lumber
Always add a waste allowance. Standard practice is to add 10–20% to your calculated board footage to account for defects, miscuts, and material lost to surfacing. For figured or premium wood, some woodworkers add as much as 25–30% since high-value boards are too expensive to run short on.
Rough vs. S4S lumber. Rough-sawn lumber is cheaper per board foot but needs to be jointed, planed, and ripped to final dimensions — which removes material. S4S (surfaced four sides) is ready to use but priced higher. Make sure you know which you're buying when you enter dimensions.
Check for twist and bow before buying. Sight down each board before purchase. Even perfect board-foot math can't help if the board is unusable.
Buy a little extra for test cuts. For any new project involving unfamiliar joinery, finishing techniques, or precise fitting, an extra piece or two for practice cuts is well worth the cost.
Technical Notes
Formula used: Board Feet = (T" × W" × L') ÷ 12, where T is thickness in inches, W is width in inches, and L is length in feet. Non-inch/foot units are converted before calculation.
Nominal vs. actual dimensions: This calculator uses whatever dimensions you enter — it does not automatically adjust for the difference between nominal and actual lumber sizes. For the most accurate cost estimate, use actual measured dimensions rather than the nominal size printed on the lumber.
Price accuracy: The cost output is only as accurate as the price per board foot you enter. Lumber prices change frequently — always confirm current pricing with your supplier before finalizing a budget.