Hardwood is sold and priced by rough thickness.
Grade drives waste more than anything else.
For weight only.
Part 1
Advanced options
0 = use the grade default.
Mills quote this way. 0 to ignore.
Included in the waste figure.
0 to skip. Small end, inside bark.
This board foot calculator works backwards from your finished parts — through the thickness the planer takes off and the waste your grade of lumber carries — to the rough footage you actually have to order.
The short answer
A board foot is 144 cubic inches — thickness × width × length ÷ 144, in inches. It’s a volume, so a 1×12 at 8 ft is 8 board feet while a 1×6 at the same length is only 4.
But the number you order isn’t the number you measured. A ¾ in tabletop needing 11.25 BF of finished wood takes 18 BF ordered — a 62% yield — because you pay on rough thickness and lose more to grade.
On this page
How to use this board foot calculator
Enter your parts one at a time — quantity, thickness, width and length. Add as many as your cut list needs.
The header toggle is the important control:
- Finished sizes — the dimensions you want when the piece is done. The calculator adds surfacing loss and grade waste to tell you what to buy.
- Rough sizes — you’re already working in rough dimensions and just want the footage.
Leave stock thickness on “choose the thinnest that works” and it picks the cheapest quarter that will still dress to your thickest part. That’s the single most useful thing here, and it’s where most first orders go wrong.
The formula
BF = Thickness × Width × Length ÷ 144 (all inches)
BF = Thickness × Width × Length ÷ 12 (length in feet)
One board foot = 144 cubic inches — a foot square, an inch thick
Worked example — tabletop, 36 × 60 in, ¾ in finished, 4/4 FAS red oak
The quarter system
Hardwood thickness is written in quarters of an inch, describing the rough-sawn board before any surfacing. It’s the NHLA convention and it catches everyone once.
| Called | Rough | Dressed S2S | Lost | % lost |
|---|---|---|---|---|
| 4/4 | 1 in | 13/16 in | 3/16 in | 19% |
| 5/4 | 1¼ in | 1¹⁄₁₆ in | 3/16 in | 15% |
| 6/4 | 1½ in | 1⁵⁄₁₆ in | 3/16 in | 12% |
| 8/4 | 2 in | 1¾ in | ¼ in | 12% |
| 10/4 | 2½ in | 2¼ in | ¼ in | 10% |
| 12/4 | 3 in | 2¾ in | ¼ in | 8% |
| 16/4 | 4 in | 3¾ in | ¼ in | 6% |
4/4 loses the largest share — 19% — because the planer takes a fixed amount off each face regardless of how thick the board started. On 16/4 that same cut is only 6%.
You are charged on the rough thickness whatever happens afterwards. That isn’t a yard overcharging you; the tree was cut at that thickness and the surfacing is a service performed on wood you already own.
The 4/4 trap
“Four-quarter” means one inch, so it sounds like the obvious choice for a one-inch part. It isn’t. Rough 4/4 dresses to 13/16 in, and no amount of careful milling gets you back the 3/16 the planer removed.
For a full inch finished you must buy 5/4, which dresses to 1¹⁄₁₆ and leaves a little to work with. That’s 25% more board feet for the same finished part — a real cost, and one to find out about before ordering rather than after.
The calculator’s auto-pick handles this. Ask for a 1 in finished part and it selects 5/4, not 4/4:
| Finished thickness needed | Buy | Dresses to |
|---|---|---|
| ¾ in | 4/4 | 13/16 in |
| 13/16 in | 4/4 | 13/16 in |
| 1 in | 5/4 | 1¹⁄₁₆ in |
| 1¼ in | 6/4 | 1⁵⁄₁₆ in |
| 1½ in | 8/4 | 1¾ in |
| 2 in | 10/4 | 2¼ in |
Where the wood actually goes
Three things sit between what your drawing says and what you write on the order, and most calculators model none of them.
Step one
11.25 BF
The finished parts. What ends up in the piece you build, measured off the cut list.
Step two
15.00 BF
What you’re charged for. Priced on 1 in rough although the part is ¾ — a third more, before anything else.
Step three
18.00 BF
What to order. Plus 20% for kerf, squaring rough edges, defect cuts and end trim on FAS stock.
Overall that’s a 62% yield. Roughly two-thirds of what you buy ends up in the work, and the rest is shavings, offcuts and rejected boards. That is normal for hardwood, not a sign of anything going wrong — but it explains why a project costs noticeably more than a naive board-foot sum suggests.
Waste is set by grade, not by a rule of thumb
“Add 10%” is softwood advice. Hardwood waste depends almost entirely on what you’re allowed to cut around.
| Grade | Waste | Order for 15 BF rough | Why |
|---|---|---|---|
| FAS / Select | 20% | 18.0 BF | Mostly clear. Kerf, squaring and end trim only |
| #1 Common | 32% | 19.8 BF | More knots to cut around, shorter clear runs |
| Character / knotty | 40% | 21.0 BF | You’ll reject whole sections |
| Figured | 45% | 21.8 BF | Boards rejected for grain match, not defects |
#1 Common is often better value than the grade names suggest — you pay considerably less per board foot and the extra waste doesn’t always cancel it out, particularly on smaller parts where you can work around defects easily. On long clear runs FAS usually wins.
With figured stock — curly maple, quilted sapele — buy the whole job at once, from one flitch if you can. The waste there isn’t defects, it’s boards that don’t match, and matching a second purchase to the first is close to impossible.
Board feet versus linear feet
These get confused constantly, and the difference can be a factor of two.
| Board | Linear feet | Board feet |
|---|---|---|
| 1×6 at 8 ft | 8 | 4.0 |
| 1×12 at 8 ft | 8 | 8.0 |
| 2×6 at 10 ft | 10 | 10.0 |
| 2×12 at 16 ft | 16 | 32.0 |
Linear feet measures length only. Board feet measures volume. Two boards of the same length can differ by four times in board feet. When a price is quoted “per foot”, ask which — on a 1×6 it’s a factor of two, and on a 2×12 it’s a factor of two the other way.
Softwood works differently
Dimensional softwood is sold by the piece at nominal sizes, and when it is figured in board feet, the yard uses the nominal dimensions — not the actual dressed ones.
A 2×4 at 8 ft
So for softwood pricing, use nominal. For hardwood, use the rough quarter thickness. Both conventions charge you for wood you don’t entirely receive, and both are standard practice rather than sharp dealing.
MBF and mill pricing
Mills and wholesalers quote in MBF — thousand board feet, from the Roman numeral M. Divide by 1,000 for the per-board-foot price:
- $850/MBF = $0.85 per BF
- $1,200/MBF = $1.20 per BF
- $4,500/MBF = $4.50 per BF
Retail hardwood dealers price per board foot; mills price per MBF, usually with a minimum order that makes it worthwhile. The calculator accepts either.
Scaling logs
Estimating what a log will yield is a different problem — a round log doesn’t cut into rectangles without loss. The Doyle rule is the common one in the eastern and southern US:
BF = (D − 4)² × L ÷ 16
D = small-end diameter inside the bark, inches · L = log length, feet
| Log | Doyle BF |
|---|---|
| 12 in × 12 ft | 48 |
| 16 in × 12 ft | 108 |
| 20 in × 16 ft | 256 |
| 24 in × 16 ft | 400 |
Doyle under-estimates small logs badly and over-estimates large ones — the “− 4” is a fixed slab allowance that hurts a 12 in log far more than a 24 in one. Scribner and International ¼-inch rules are more accurate; International is the most so. Which one applies is regional, and it affects what you’re paid for standing timber.
Board foot mistakes to avoid
- Buying 4/4 for a 1 in finished part. It dresses to 13/16. You need 5/4.
- Using dressed thickness in the formula. Hardwood is priced on rough.
- Using actual dimensions for softwood. Under-counts a 2×4 by 34%.
- Confusing board feet with linear feet. One is volume, one is length.
- Adding 10% waste. That’s softwood thinking — hardwood runs 20–45% by grade.
- Ordering figured wood in two batches. The second lot won’t match.
- Forgetting width loss on S4S. Edges get milled too, not just faces.
- Measuring live-edge boards at their widest. Use the average width.
Frequently asked questions
How do you calculate board feet?
Thickness × width × length ÷ 144, with all three in inches. If the length is in feet, divide by 12 instead. A board 2 in thick, 6 in wide and 10 ft long is 2 × 6 × 10 ÷ 12 = 10 board feet. One board foot is 144 cubic inches.
What does 4/4 mean?
Four quarters of an inch — nominally 1 inch, describing the rough-sawn thickness before surfacing. It’s the NHLA convention for hardwood. 5/4 is 1¼ in, 6/4 is 1½, 8/4 is 2. After surfacing on both faces, 4/4 finishes at about 13/16 in.
Why is my 4/4 board not 1 inch thick?
Because it’s been surfaced. The planer removes roughly 3/16 in across both faces, taking a rough 1 in board down to about 13/16. You’re still charged on the 1 in rough thickness, which is standard practice — the board was sawn at that size and surfacing is work done on wood you already bought.
What thickness do I buy for a 1 inch finished part?
5/4, not 4/4. Rough 4/4 dresses to about 13/16 in, so it can never give a full inch. 5/4 dresses to 1¹⁄₁₆ and leaves a little to work with. It costs 25% more in board feet, and it’s the most common first-time buying mistake.
How much waste should I add?
It depends on grade. 20% for FAS or Select, 32% for #1 Common, 40% for character or knotty stock, and 45% for figured wood where boards get rejected for grain match rather than defects. The 10% figure people quote is softwood advice and is too low for hardwood.
What is the difference between board feet and linear feet?
Board feet measures volume; linear feet measures length only. A 1×12 at 8 ft is 8 board feet but a 1×6 at 8 ft is only 4 — same linear length, half the volume. When a price is quoted per foot, always ask which is meant.
How many board feet in a 2×4?
An 8 ft 2×4 is 5.33 board feet using nominal dimensions, which is how yards price it. Using the actual dressed size of 1½ × 3½ gives 3.50 board feet — 34% less — but that isn’t what you’ll be charged. Use nominal for softwood pricing.
What does MBF mean?
Thousand board feet, from the Roman numeral M. Mills and wholesalers quote this way, so $1,200 per MBF is $1.20 per board foot. Retail hardwood dealers usually price per board foot instead.
How much does a board foot weigh?
It depends on species and moisture content. Kiln-dried averages run about 2.8 lb for poplar, 3.2 for cherry, 3.5 for walnut and ash, 3.9 for red oak and 4.0 for hard maple. Green lumber is considerably heavier. Density varies 10–15% within a species.
What is the Doyle rule?
A log scaling rule estimating board feet from a log: (diameter − 4)² × length ÷ 16, using the small-end diameter inside the bark. It’s common in the eastern and southern US, but it under-estimates small logs and over-estimates large ones. Scribner and International ¼-inch rules are more accurate.
What is S2S and S4S?
Surfaced two sides means both faces are planed flat while the edges stay rough, so you set the final width. S4S is surfaced on all four sides and ready to use. S2S is often the sweet spot — flat faces for layout at less cost than fully milled stock. Board feet are charged on the rough size either way.
Can I use this board foot calculator in metric?
Dimensions are in inches, since board feet is an imperial unit and hardwood is sold that way in North America. One board foot is 0.00236 cubic metres, so 424 board feet make a cubic metre. Multiply inches by 25.4 for millimetres.
Standards and sources
- NHLA quarter-thickness convention for rough hardwood, and standard surfaced dimensions for S2S stock
- American Softwood Lumber Standard PS 20 for nominal versus actual softwood dimensions
- Waste allowances by grade compiled from published woodworking estimating guidance; FAS at 20% rising to 45% for figured stock
- Weight per board foot from Wood Database species averages at typical kiln-dried moisture content
- Doyle log rule as commonly applied in the eastern and southern United States
- Surfaced dimensions vary between mills — confirm with your supplier before ordering to a critical thickness
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How this board foot calculator works out its numbers
Each part is thickness × width × length ÷ 144, multiplied by quantity. That gives the finished volume — what ends up in the piece.
When you’re working from finished sizes, the calculator then recomputes the footage using the rough thickness of the stock you’ll buy, because that’s what the yard charges on. A ¾ in part cut from 4/4 is billed at 1 in, which is a 33% uplift before anything else happens. Grade waste is applied last, on the rough figure.
Auto stock selection walks the quarter thicknesses in order and picks the first one whose dressed dimension still covers your thickest part. That’s why asking for a full 1 in finished returns 5/4 rather than 4/4 — the surfaced dimension is what has to clear, not the nominal one.
Surfaced dimensions vary between mills. The figures here are the common ones, but some mills surface heavier than others, and a board that arrives at ¾ instead of 13/16 will ruin a tight cut list. If a thickness is critical, confirm it with your supplier before ordering, and buy a little extra so you have something to test the planer on.