If you've ever stood in a hardwood lumber yard wondering why the price tags show dollars per "board foot" instead of per board, you're not alone. Board feet can be confusing—until you understand what you're actually paying for.
This calculator takes the guesswork out of lumber math. Enter your board dimensions, tell it how many pieces you need, plug in your local price, and you'll know exactly what your lumber will cost before you load up the truck. No more mental math at the lumber yard, no more surprise totals at checkout.
Whether you're pricing out walnut for a dining table or figuring how many deck boards fit your budget, getting the board footage right means buying smart—not just buying.
What Is a Board Foot?
A board foot is simply a way to measure lumber volume. One board foot equals 144 cubic inches of wood—picture a piece that's 1 inch thick, 12 inches wide, and 12 inches long.
But here's what actually matters: board feet let you compare apples to apples when buying lumber.
A wide, thin board and a narrow, thick board might look completely different, but if they both contain 6 board feet, they represent the same amount of wood—and should cost roughly the same. That's why lumber yards use this measurement. It's fair pricing based on what you're actually getting.
The practical reality:
- Buying a rough-sawn 8/4 walnut slab? You're paying by the board foot.
- Picking up 2x4s at Home Depot? They're priced by the piece (linear foot).
- Shopping for hardwood flooring? Usually priced per square foot.
Different contexts use different measurements. Board feet dominate when you're buying lumber from hardwood dealers and sawmills—the places where serious woodworkers shop.
The Board Foot Formula
Here's the math behind every lumber purchase:
Board Feet = (Thickness × Width × Length) ÷ 144
All measurements in inches. That 144 converts cubic inches to board feet.
Most people find this version easier when length is in feet:
Board Feet = (Thickness × Width × Length in feet) ÷ 12
Let's run a real example:
You're eyeing a cherry board that's 6/4 thick (1.5 inches), 8 inches wide, and 10 feet long.
- Board Feet = (1.5 × 8 × 10) ÷ 12
- Board Feet = 120 ÷ 12
- Board Feet = 10
At $7.50 per board foot for cherry, that single board costs $75. Now you know whether it fits your budget before you commit.
Pro tip: Lumber dealers round up. A board measuring 9.3 board feet gets charged as 10. Factor this into your estimates.
How to Use This Calculator
1. Enter your board thickness. For hardwoods, use the actual rough thickness (1" for 4/4, 1.5" for 6/4, 2" for 8/4). For dimensional lumber from home centers, use the real dimension—a "2x4" is actually 1.5 inches thick.
2. Enter the width. Same rule: actual measurements. That "1x6" pine board? It's really 0.75" × 5.5".
3. Enter the length. Pick whatever unit is easiest. Buying 8-foot boards? Type 8 and select feet. Working in metric? The calculator handles that too.
4. Set your quantity. Building a project that needs 12 boards? Enter 12 and get your total instantly instead of multiplying in your head.
5. Add the price per board foot. Call your lumber yard or check their website. Plug in their price and see your estimated total. No more sticker shock at the register.
6. Read your results. You'll see total board feet and estimated cost. Screenshot it, bring it to the lumber yard, and buy with confidence.
Common Lumber Sizes: Quick Reference
Stop calculating these every time. Here's what standard dimensional lumber actually contains:
Size | Real Dimensions | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|---|
2×4 | 1.5" × 3.5" | 2.67 bf | 3.33 bf | 4.00 bf | 5.33 bf |
2×6 | 1.5" × 5.5" | 4.17 bf | 5.21 bf | 6.25 bf | 8.33 bf |
2×8 | 1.5" × 7.25" | 5.50 bf | 6.88 bf | 8.25 bf | 11.00 bf |
2×10 | 1.5" × 9.25" | 7.00 bf | 8.75 bf | 10.50 bf | 14.00 bf |
2×12 | 1.5" × 11.25" | 8.50 bf | 10.63 bf | 12.75 bf | 17.00 bf |
4×4 | 3.5" × 3.5" | 6.53 bf | 8.17 bf | 9.80 bf | 13.07 bf |
For hardwood thickness (rough-sawn):
Notation | Actual Thickness | What You Get After Planing | ||
|---|---|---|---|---|
4/4 | 1" | About 13/16" (0.8125") | ||
5/4 | 1.25" | About 1-1/16" (1.0625") | ||
6/4 | 1.5" | About 1-5/16" (1.3125") | ||
8/4 | 2" | About 1-3/4" (1.75") | ||
12/4 | 3" | About 2-3/4" (2.75") |
Why this matters: You pay for 8/4 lumber (2 inches), but after surfacing you've got 1.75 inches. Plan your project dimensions around the finished thickness, not the rough thickness.
Practical Examples
Building a Walnut Coffee Table
The project: A 48" × 24" tabletop from 6/4 walnut, plus 4 tapered legs.
The tabletop: You'll need boards totaling at least 26 inches of width (accounting for saw kerfs and jointing) to get a 24-inch finished top.
Three boards: 6/4 × 9" × 54" each
- Per board: (1.5 × 9 × 54) ÷ 144 = 5.06 board feet
- Three boards: 15.19 board feet
The legs (from 8/4 stock): Four blanks at 2" × 3" × 18"
- Total: (2 × 3 × 18 × 4) ÷ 144 = 3 board feet
Project total: 18.19 board feet of walnut
At $12 per board foot, your lumber budget is approximately $218 before tax. Add 15% waste factor, and plan for around $250 in lumber.
Pricing Out a Deck
The project: 12' × 16' deck using pressure-treated lumber.
Decking (5/4 × 6 boards, 12 ft long): You'll need about 32 boards to cover 192 square feet with proper spacing.
- Per board: (1.25 × 5.5 × 144) ÷ 144 = 6.88 board feet
- 32 boards: 220 board feet
Joists (2×8 × 12 ft): Using 16" spacing, you need 13 joists.
- Per joist: 8.25 board feet
- 13 joists: 107 board feet
Framing total: Roughly 450 board feet including rim joists, blocking, and ledger board.
At $2.50/bf for pressure-treated, your rough lumber estimate is $1,125. Reality check: most people buy deck lumber by the piece, not board foot—but knowing the board footage helps you compare quotes from different suppliers.
The "Should I Drive Farther?" Decision
Your local home center sells red oak at $8.75 per board foot. A hardwood dealer 45 minutes away charges $6.25—but you'd burn gas and time.
For a small project (20 board feet):
- Local: $175
- Drive: $125 + gas (~$15) + 1.5 hours = $140 total
Savings: $35. Probably not worth your Saturday morning.
For a large project (150 board feet):
- Local: $1,312.50
- Drive: $937.50 + gas = ~$955
Savings: $357. Now we're talking. Make the drive.
The breakeven point for most trips is around 50-75 board feet. Below that, convenience wins. Above that, the specialty dealer usually makes sense—plus you'll get better selection and can hand-pick your boards.
Estimating Rough-Sawn Lumber
A local sawyer offers fresh-cut white oak for $3 per board foot. Great deal—but the boards are rough and wet.
What to expect:
- 8/4 rough will dry to about 1.9" and plane to 1.75"
- Boards may warp, check, or develop defects during drying
- Plan for 20-30% waste, not the usual 10-15%
Your 100 board foot purchase:
- Cost: $300
- Usable after drying/milling: ~70-80 board feet
- Effective cost: $3.75-$4.30 per usable board foot
Still cheaper than kiln-dried from a dealer ($6-8/bf), but only if you have space to stack and sticker it for 6-12 months. Not everyone does.
Board Feet vs. Linear Feet: The Confusion That Costs Money
These two measurements trip up even experienced buyers. Here's the difference that matters for your wallet:
Linear feet = length only. An 8-foot board is 8 linear feet, period. Doesn't matter if it's a 2×4 or a 2×12.
Board feet = volume. That same 8-foot board could be 2.67 board feet (if it's a 2×4) or 8.5 board feet (if it's a 2×12).
Real-world trap: A lumber yard quotes you "$3 per foot" for cedar. Per linear foot or per board foot?
If you're buying 2×6×10 cedar boards:
- At $3 per linear foot: $30 per board
- At $3 per board foot: $15.63 per board
That's nearly double the price for the same lumber. Always ask: "Is that per board foot or per linear foot?"
General rule:
- Home centers (Home Depot, Lowe's) = linear feet or per piece
- Hardwood dealers and sawmills = board feet
- Specialty softwood yards = could be either—ask first
Smart Lumber Buying Tips
Calculate before you shop. Know your board footage before you leave the house. Walking into a lumber yard without a number is like grocery shopping without a list—you'll overspend.
The 15% rule is real. Add 15% to your calculated needs. That perfect board might have a hidden split. You might miscut something. The grain might not match. Extra lumber is insurance; running short halts your project.
Understand S2S, S3S, and S4S.
- Rough: Fresh from the sawmill, no surfacing. Cheapest, but you'll need a planer.
- S2S (surfaced two sides): Faces are flat, edges are rough. You set the final width.
- S4S (surfaced four sides): Ready to use. Most expensive, but no machines needed.
S2S often hits the sweet spot—you get flat faces for layout and glue-ups but pay less than fully milled stock.
Ask about FAS, Select, and #1 Common. Hardwood grades affect price and yield:
- FAS (First and Seconds): Premium, mostly clear. Highest price, lowest waste.
- Select: One good face. Great for projects where one side doesn't show.
- #1 Common: More knots and character. Cheapest, but plan for more waste.
For furniture, Select often gives the best value. You're not paying for two perfect faces when the bottom never shows.
Buy in person when possible. Online lumber prices don't include the ugly boards they'll ship you. At a dealer, you can flip through the stack and pick the grain patterns you want. That control is worth the trip.