🪵 Board Foot Calculator
Calculate lumber volume and cost for hardwood purchases
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"First thing I tell every customer: board feet ain't linear feet. I've watched folks walk in wanting '40 feet of walnut' for shelves, then get sticker shock when I tell them that's actually 26.7 board feet at 8/4 thickness and costs $280, not $120. The math trips everyone up at first. Here's my shortcut: a 1-inch thick board that's 1 foot wide and 1 foot long is 1 board foot. Everything scales from there. And never ask for exact widths—hardwood comes random width. I can't sell you 'ten 6-inch boards.' I can sell you boards that range 5-8 inches and you pick through the stack. That's how hardwood works."
🧮 Understanding Board Feet
If you've only bought dimensional lumber (2x4s, 2x6s) from Home Depot, board feet will seem weird. That's okay—it confused me too the first time I walked into a lumber yard asking for "eight feet of oak." The guy looked at me like I'd spoken gibberish.
The Formula
Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12
Example: You want a board that's 1 inch thick, 8 inches wide, and 10 feet long:
- 1 × 8 × 10 = 80
- 80 ÷ 12 = 6.67 board feet
If that same board was 2 inches thick (8/4 instead of 4/4), you'd have 13.33 board feet—double the volume, double the cost.
Why This Matters for Your Wallet
Hardwood prices are all over the map depending on species and grade. Red oak might run $4.50/bf while walnut is $12/bf. When you're building a walnut dining table and need 35 board feet, that's $420 in lumber alone. Mess up your math and buy 50 board feet? You just spent an extra $180.
I learned this lesson building my first workbench. I needed 4/4 maple for the top, calculated 22 linear feet, bought it, got home, and realized I'd actually needed 30 board feet because my top was going to be 16 inches wide. Had to make a sheepish trip back to the lumber yard the next day.
Rough vs. Surfaced Thickness
Here's where it gets sneaky: most hardwood is sold rough-sawn (straight from the sawmill, with rough surfaces). When you buy 4/4 rough, you're getting boards that are a full 1 inch thick, maybe 1-1/16.
If you buy it surfaced (S2S = surfaced two sides, or S4S = surfaced four sides), the lumber yard has run it through a planer. Your 4/4 board is now 13/16 or 7/8 inch after they've cleaned it up. But here's the kicker: you still pay for the original rough thickness, not the finished thickness.
Why? Because they had to buy a full 1-inch thick board to give you that 13/16-inch board. The sawdust from planing is your problem, not theirs. This is standard across the industry—not a rip-off, just how it works.
Sam Peterson
Hardwood Lumber Specialist
22 years at Woodworkers Source, certified lumber grader
⚠️ 5 Board Foot Mistakes That'll Cost You
1. Confusing Linear Feet with Board Feet
The Mistake: "I need 20 feet of cherry for a mantel" vs. "I need 20 board feet of cherry."
Why It Matters: If that mantel is 10 inches wide and you want 8/4 (2-inch) thick stock, 20 linear feet is actually 33.3 board feet. At $9/bf, that's $300, not the $180 you budgeted thinking 20 feet = 20 bf.
The Fix: Always calculate total board feet needed for your project before walking into the lumber yard. Thickness × Width × Length ÷ 12. Write it down. Bring a calculator.
2. Ordering Exact Widths
The Mistake: "I need ten boards exactly 7.5 inches wide."
Why It Won't Work: Trees don't grow in standard sizes. Hardwood is sold random width—boards come 4, 6, 8, 10, 12 inches wide, whatever the log yielded. You can't special order specific widths unless you're buying 500 board feet and willing to pay a premium for selectivity.
The Fix: Oversize your order slightly. Need 7.5-inch finished widths? Buy boards that are 8-10 inches wide and rip them down. Factor in 10-15% waste for cutoffs and defects. This is normal—every woodworker does it.
3. Not Accounting for Planing Loss
The Mistake: Buying 4/4 (1-inch) rough lumber expecting to end up with 1-inch thick finished boards.
What Actually Happens: You lose about 1/8 inch per face when surfacing. Planing both faces of a rough 1-inch board gives you 3/4 inch finished. If your project requires 1-inch finished thickness, you needed to buy 5/4 or even 6/4 stock.
The Fix: For rough lumber, add 1/4 to 3/8 inch to your required finished thickness. Want 1.5-inch table legs? Buy 8/4 (starts at 2 inches), not 6/4 (starts at 1.5 inches).
4. Falling for "Sale Prices" Without Checking Per-BF Cost
The Mistake: "Oak boards on sale! $35 each!" Sounds great, but...
The Reality: If those are 6/4 boards, 6 inches wide, 8 feet long, that's 6 board feet per board. $35 ÷ 6 = $5.83/bf. Meanwhile the "regular price" lumber across the aisle is $4.50/bf. You're paying more for the "sale."
The Fix: Always calculate the per-board-foot price. It's the only way to compare apples to apples. Lumber yards know most customers don't do this math, and pricing gets real creative during "sales."
5. Forgetting About Defects and Waste
The Mistake: Your project needs exactly 25 board feet, so you buy exactly 25 board feet.
What Goes Wrong: Board three has a 10-inch knot you can't use. Board seven has a split end. Board nine has sapwood you're cutting off. Suddenly your 25 bf has become 21 bf of usable wood, and your project is 4 bf short.
The Fix: Add 15-20% overage for select grade, 25-30% for #1 common grade. Defects happen. Better to have leftovers for your next project than to realize you're 3 bf short on Sunday when the lumber yard is closed.
💰 Hardwood Pricing Guide (2024)
Prices vary by region, grade, and width. Wider boards (12+ inches) command premium prices. These are approximate ranges for FAS or Select grade at retail lumber yards:
| Species | $/Board Foot | Notes |
|---|---|---|
| Red Oak | $3.50 - $6.00 | Most affordable domestic hardwood |
| White Oak | $4.50 - $8.00 | Slightly more than red oak, better rot resistance |
| Hard Maple | $4.00 - $7.00 | Great for cutting boards and workbenches |
| Cherry | $6.00 - $10.00 | Darkens beautifully with age |
| Black Walnut | $8.00 - $14.00 | Premium domestic, prices spiked in recent years |
| Ash | $5.00 - $8.00 | Getting scarce due to emerald ash borer |
| Mahogany (African) | $8.00 - $12.00 | Imported, check for FSC certification |
| Purpleheart | $12.00 - $18.00 | Exotic, vibrant purple color |
| Figured Wood (any species) | +50-200% | Bird's eye, quilted, curly = premium prices |
Hidden Costs to Watch For
- Surfacing fees: $0.50-1.50/bf to run rough boards through their planer
- Ripping fees: Some yards charge to rip wide boards to your width
- Minimum purchase: Some wholesalers require 100+ bf minimum orders
- Delivery: Can run $50-150 depending on distance and volume
- Selection fees: Some yards charge extra if you hand-pick boards vs. "mill run"
❓ Frequently Asked Questions
What is a board foot and how is it calculated?
A board foot is a unit of volume for lumber equal to 144 cubic inches—imagine a board that's 1 inch thick, 12 inches wide, and 12 inches long. The formula is: Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12. For example, a 1-inch thick board that's 6 inches wide and 8 feet long equals (1 × 6 × 8) ÷ 12 = 4 board feet. Hardwood lumber is almost always priced per board foot, not per linear foot like dimensional lumber.
Why is hardwood sold by board feet instead of linear feet?
Hardwood comes in random widths and varying thicknesses, unlike standardized dimensional lumber (2x4s, 2x6s). Selling by board feet accounts for the total wood volume, making pricing fair regardless of board dimensions. A 4-inch wide board and an 8-inch wide board at the same length contain different amounts of wood, so they should cost different amounts. Board feet measure total volume, ensuring you pay for what you're actually getting.
Do I use nominal or actual thickness for board feet?
For rough-sawn hardwood, use the actual thickness as measured. For surfaced (S2S or S4S) lumber, lumber yards typically calculate board feet using the nominal (rough) thickness before planing, not the finished thickness. So a board sold as 4/4 (one inch thick when rough) but planed down to 13/16 inch is still charged at 1 inch for board foot calculations. This is industry standard—you're paying for the wood that was originally there, not just what's left after milling.
How much does hardwood cost per board foot?
Prices vary widely by species, grade, and region. As of 2024: Red Oak runs $3-6/bf, White Oak $4-8/bf, Walnut $8-14/bf, Cherry $6-10/bf, Maple $4-7/bf; exotic species like Purpleheart or Wenge can run $12-20/bf. Select grade costs more than common grade. Wider boards command premium prices. Local sawmills often beat retail lumber yards by 30-40%. Always ask for the per-board-foot price before buying—some yards advertise low prices but surprise you with hidden fees.
What does 4/4, 5/4, 6/4, 8/4 mean in hardwood lumber?
These are quarter measurements representing rough thickness in quarters of an inch. 4/4 (pronounced "four-quarter") = 1 inch thick rough, 5/4 = 1.25 inches, 6/4 = 1.5 inches, 8/4 = 2 inches, 12/4 = 3 inches. After surfacing (planing smooth), you lose about 1/4 inch: 4/4 rough becomes 3/4 inch S2S, 5/4 becomes 1 inch S2S, 8/4 becomes 1.75 inches S2S. If you need finished 1-inch thick wood, buy 5/4 or 6/4 stock and plane it yourself, not 4/4.
How do I find cheap hardwood?
Skip big-box stores (Lowe's, Home Depot) which charge 2-3x retail. Find local sawmills via Google Maps—many sell direct to the public at wholesale prices. Check Craigslist for tree services; when they take down a walnut tree, they often sell the logs dirt cheap to anyone with a chainsaw mill. Join woodworking clubs; members often know local sources. Buy "shorts" (8-foot boards) or lower grades (#1 Common instead of FAS/Select) if your project can work around knots. And always ask lumber yards about their "cull pile"—scratched, stained, or odd-width boards sold 50% off.