Board Feet Calculator
Calculate board feet for finished lumber or estimate yield from standing and felled logs. Built for woodworkers, sawmill operators, foresters, and lumber buyers who need answers in seconds — not spreadsheets.
Lumber mode — use this for finished, surfaced, or rough-sawn boards where you already know the thickness, width, and length. Enter nominal sizes (e.g. a 2×4) unless you're working from milled actual dimensions.
Log mode — estimates the board feet a log will yield. Measure the small-end diameter inside bark and the merchantable length. Results vary by log rule because each rule was designed for different regions and saw technologies.
Batch mode — add multiple boards one by one and we'll sum the total board feet. Useful when buying a hardwood pack or reconciling a mill invoice.
Tip: Use the same units (inches for thickness/width, feet for length) for the cleanest result. Need help reading thickness? See the 4/4 5/4 6/4 8/4 thickness chart below ↓
What Is a Board Foot?
A board foot (abbreviated BF or bd. ft.) is the standard volumetric unit for lumber in the United States, Canada, the Philippines, and several other markets. One board foot equals 144 cubic inches of wood — the exact volume of a board that is 1 inch thick, 12 inches wide, and 1 foot long.
Board Foot vs Linear Foot vs Square Foot
These three units are often confused because hardware stores price softwoods, hardwoods, and dimensional lumber inconsistently. The distinction matters when you compare quotes:
- Linear foot — measures length only. Common for trim, baseboards, and dimensional 2× lumber sold by the piece.
- Square foot — measures area (length × width). Used for sheet goods like plywood, MDF, or flooring.
- Board foot — measures volume (length × width × thickness). The standard for rough hardwoods, exotic species, and anything sold by the pack.
Why Lumber Is Sold in Board Feet
Hardwoods aren't milled to a single fixed thickness the way construction softwoods are. Walnut, white oak, cherry, and maple come from sawmills in random widths and varying thicknesses — 4/4, 5/4, 6/4, 8/4 — so charging by the linear foot would be unfair to both seller and buyer. Pricing by volume (board feet) reflects how much wood you actually receive, regardless of how the boards are shaped.
Board Feet Formula Explained
Every board foot calculator on the internet — including this one — reduces to one of two equations. The variables are thickness (T), width (W), and length (L). Pick the formula that matches the unit of your length measurement.
Standard Formula (length in feet)
Board Feet = (T × W × L) ÷ 12
Where T and W are in inches and L is in feet. The constant 12 converts inches of length into feet.
All-Inches Formula
Board Feet = (T × W × L) ÷ 144
Use this when every dimension is in inches. The divisor 144 is the number of cubic inches in one board foot.
Worked Examples
Example 1 — A single 4/4 walnut board
A walnut plank is 1 inch thick, 8 inches wide, and 10 feet long.
(1 × 8 × 10) ÷ 12 = 6.67 BF.
Example 2 — Pricing a hardwood pack
You're quoted $4.25 per BF for 20 boards measuring 4/4 × 7" × 8'. Each board is (1 × 7 × 8) ÷ 12 = 4.67 BF. Twenty boards = 93.3 BF. Total = 93.3 × $4.25 = $396.53.
Example 3 — Rough vs surfaced lumber
Hardwood dealers usually charge for the rough dimensions before surfacing. A board listed as 4/4 may finish to 13/16" after S2S milling, but it's still sold as one board foot per (1 × 12 × 12) cubic inches of original stock. Confirm with the supplier whether your invoice is based on rough or surfaced measure.
Common Calculation Mistakes to Avoid
- Measuring after surfacing. A 2×4 measures 1.5" × 3.5" — but for BF math you use the nominal 2" × 4".
- Mixing units. Putting length in inches into the standard formula gives a result 12× too large.
- Forgetting quantity. Always multiply by the number of identical boards.
- Confusing log scale with lumber scale. A 100 BF log usually produces 180–270 BF of finished lumber. They are not interchangeable.
Nominal vs Actual Lumber Dimensions
This is the single biggest reason people get the "wrong" answer from a board foot calculator. Softwood dimensional lumber is sold under nominal names that don't match the wood you actually receive after kiln drying and surfacing.
Why a 2×4 Is Really 1.5" × 3.5"
A 2×4 leaves the sawmill close to 2 inches by 4 inches, but it loses material on every surface during drying and the four-sided planing process (S4S). By the time it reaches a lumberyard, a "2×4" measures 1.5" × 3.5". For most board-foot transactions you still use the nominal size — that's how the industry agreed to price it.
Lumber Size Reference Chart
| Nominal | Actual (dried, S4S) | BF per linear foot (nominal) |
|---|---|---|
| 1×4 | 0.75" × 3.5" | 0.33 |
| 1×6 | 0.75" × 5.5" | 0.50 |
| 1×8 | 0.75" × 7.25" | 0.67 |
| 1×10 | 0.75" × 9.25" | 0.83 |
| 2×4 | 1.5" × 3.5" | 0.67 |
| 2×6 | 1.5" × 5.5" | 1.00 |
| 2×8 | 1.5" × 7.25" | 1.33 |
| 2×10 | 1.5" × 9.25" | 1.67 |
| 2×12 | 1.5" × 11.25" | 2.00 |
| 4×4 | 3.5" × 3.5" | 1.33 |
Log Board Feet — Estimating Yield from a Log
Log board feet and lumber board feet are different units that happen to share a name. Lumber BF is a precise volume measurement of finished wood. Log BF is an estimate of how much sawn lumber a log might produce — and the estimate depends entirely on which log rule you choose.
Log rules were developed in the 19th century by foresters who needed a portable way to predict yield without milling the log. Each rule embeds assumptions about kerf width, sawing technology, and acceptable defect that may or may not match modern sawmills.
Doyle Log Rule (1837)
BF = ((D − 4) ÷ 4)² × L
Where D is the small-end diameter inside bark (inches) and L is the log length (feet). Doyle is the dominant rule in the US Midwest and Southern hardwood industries. It is mathematically simple and conservative — it undervalues small logs (under 16") and overvalues large ones. Mills that buy logs on Doyle and sell lumber on International ¼-inch frequently report "overrun" of 30% or more.
Scribner Log Scale (1846)
Scribner is a diagram-based rule that visualizes how many rectangular boards can be drawn inside a circular log end. It assumes ¼-inch kerf and ignores taper. Scribner Decimal C — rounded to the nearest 10 BF — is the standard for log sales across the US Pacific Northwest and is required for federal timber on US Forest Service lands in that region.
International ¼-inch Log Rule (1906)
Developed by Judson Clark, the International ¼-inch rule accounts for taper by dividing the log into 4-foot segments and computing yield for each. It assumes ¼-inch kerf and roughly matches the output of a modern band sawmill. Most US Forest Service inventory and Appalachian hardwood transactions use International ¼-inch because it gives the most realistic prediction of sawn yield.
Smalian's Formula
V = ((A₁ + A₂) ÷ 2) × L
Smalian's formula treats the log as a frustum and calculates true cubic volume by averaging the cross-sectional areas at each end. Common in Canadian and European forestry. We convert the cubic volume to board feet at 144 cubic inches per BF — but remember this is the log's geometric volume, not its sawn-lumber yield.
Side-by-Side Log Rule Comparison
For a single 16-inch diameter × 16-foot log:
| Rule | Estimated BF | Best For |
|---|---|---|
| Doyle | 144 BF | Larger logs in Midwest/South USA |
| Scribner | ~166 BF | Pacific Northwest timber sales |
| International ¼" | ~180 BF | Modern sawmills, Appalachia |
| Smalian's | ~304 BF | Cubic volume / research |
Log BF → Lumber BF Conversion (Yield Ratio)
Buyers often ask: "I bought a 100 BF log. How much usable lumber will I get?" The answer is almost always more than the log scale predicted — provided the rule is Doyle or Scribner.
Typical Overrun: 1.8× to 2.7×
Modern band sawmills cutting Doyle-scaled logs commonly produce 1.8 to 2.7 board feet of lumber per board foot of Doyle log scale. International ¼-inch is much closer to reality, with overrun typically under 1.2×.
What Affects Yield
Sawing Method
Live-sawing (cutting straight through) maximizes yield but produces a mix of grain orientations. Quarter-sawing produces beautiful stable boards but wastes more wood. Rift-sawing is the most wasteful but yields the highest-grade boards for furniture.
Log Defects and Taper
Sweep, crook, rot, shake, and metal embedded in the log all reduce usable yield. Taper helps log-rule estimates be more accurate because rules like International ¼-inch already model it.
Kerf Width and Drying Loss
Every saw blade removes wood as sawdust. A circular mill with a 5/16-inch kerf wastes nearly twice as much wood as a band mill with a 3/32-inch kerf. Air-drying and kiln-drying then shrink boards by roughly 7–10% across the grain.
Board Feet Quick Reference Charts
4/4, 5/4, 6/4, 8/4 Thickness Explained
Hardwood lumber is sold in quarter-inch thickness increments, expressed as a fraction over four. The numerator is the rough thickness in quarter inches before surfacing.
| Quarter measure | Rough thickness | Surfaced (S2S) thickness | Typical use |
|---|---|---|---|
| 4/4 | 1" | 13/16" | Furniture panels, cabinet doors |
| 5/4 | 1¼" | 1 1/16" | Stair treads, table tops |
| 6/4 | 1½" | 1 5/16" | Bench seats, thicker tops |
| 8/4 | 2" | 1¾" | Table legs, chair stretchers |
| 12/4 | 3" | 2¾" | Workbench tops, turning blanks |
| 16/4 | 4" | 3¾" | Architectural posts |
Common Hardwood Board BF
BF for a single board, length × actual width (nominal thickness 4/4):
| 6" wide | 8" wide | 10" wide | 12" wide | |
|---|---|---|---|---|
| 6 ft | 3.0 | 4.0 | 5.0 | 6.0 |
| 8 ft | 4.0 | 5.33 | 6.67 | 8.0 |
| 10 ft | 5.0 | 6.67 | 8.33 | 10.0 |
| 12 ft | 6.0 | 8.0 | 10.0 | 12.0 |
Frequently Asked Questions
How do I calculate board feet for a 2×4?
Use the nominal dimensions 2 inches thick by 4 inches wide. For an 8-foot 2×4: (2 × 4 × 8) ÷ 12 = 5.33 board feet. Don't substitute the actual 1.5" × 3.5" — pricing is based on nominal size.
Is a board foot the same as a linear foot?
No. A linear foot measures only length. A board foot measures volume: 144 cubic inches. A 12-foot 1×6 is 12 linear feet but 6 board feet.
Which log rule is most accurate?
International ¼-inch is widely considered the closest to modern sawmill yield. Doyle is conservative and well-suited to traditional hardwood markets in the Midwest and South. Scribner remains standard for federal timber in the US Pacific Northwest.
Can I calculate board feet in metric (cm or meters)?
Board feet is by definition an imperial unit. Convert your metric measurements: 1 cm = 0.394 inches, 1 m = 3.281 feet. Or use our cubic-meter equivalents in the result panel. 1 BF ≈ 0.00236 m³.
How many board feet are in one cubic foot?
Exactly 12 board feet per cubic foot. Since 1 BF = 144 cubic inches and 1 cubic foot = 1,728 cubic inches, 1,728 ÷ 144 = 12.
Why does my mill's count differ from the calculator?
Mills sometimes use tally rules (random width, random length) that round each board to the nearest half-inch, or they may be charging on surfaced rather than rough measure. Ask the seller which measurement system the invoice uses.
Is this calculator free?
Yes. No signup, no tracking beyond standard analytics, no daily usage caps. We keep the site free because we believe accurate measurement should be accessible to every woodworker and sawyer.
About This Calculator
This board feet calculator implements the four most widely recognized formulas in North American forestry — Doyle, Scribner Decimal C, International ¼-inch, and Smalian's — alongside the standard lumber formula. Calculations run entirely in your browser; nothing is sent to a server.
Formulas are sourced from the USDA Forest Service General Technical Report NE-191, NHLA grading rules, and decades of accepted forestry practice. We update the page when sawmill conventions change or when readers send corrections.
Have feedback? Get in touch — we read every message.