Board Feet Calculator

How to Use This Board Feet Calculator

The calculator supports three workflows — pick the mode that matches what's in front of you, enter the numbers, and read the volume, cost, and metric equivalents. No signup, no export, no data sent anywhere.

Step 1 — Choose Your Mode

• Lumber mode — for finished, surfaced, or rough-sawn boards where the thickness, width, and length are already known. Best for hardware-store lumber, hardwood packs, and any board that has already been sawn.
• Log mode — for standing timber or felled logs where you know the small-end diameter and merchantable length. Pick the log rule (Doyle, Scribner, International ¼-inch, or Smalian's) that matches your region or contract.
• Batch mode — for reconciling a mill invoice, adding up a random-width pack, or estimating a whole material list. Add board rows one by one and see the running total.

Step 2 — Enter Measurements Correctly

• Use nominal thickness and width for dimensional softwood (a 2×4 stays 2 × 4, not 1.5 × 3.5). Use actual dimensions only when your invoice or spec sheet says so.
• Length is normally in feet. Switch the length-unit selector to inches if you're measuring shorts, offcuts, or trim pieces.
• For logs, always measure the small-end diameter inside the bark — the industry-standard reference every log rule expects.
• Enter a per-BF price only if you want the cost line to appear in the result. Leave it blank for a pure volume calculation.

Step 3 — Read the Result

The result panel shows the board-foot volume, the cubic-inch and cubic-meter equivalents, and — if you supplied a price — the total cost. Log mode also shows which rule was used and a plain-language yield note so you can sanity-check the number before signing the invoice.

Keyboard Tips and Common Shortcuts

• Press Tab to jump between fields — the same order as the visual layout.
• Batch mode: use Enter after typing the last field to add the row without reaching for the mouse.
• All numbers accept decimals — enter 1.25 for 1¼-inch stock, 10.5 for a 10-foot 6-inch length.

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)

Where T and W are in inches and L is in feet. The constant 12 converts inches of length into feet.

All-Inches Formula

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.

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)

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

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:

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.

Common Hardwood Board BF

BF for a single board, length × actual width (nominal thickness 4/4):

Board Feet in Everyday Projects

Board feet aren't an abstract unit — they show up on every lumber invoice, sawmill quote, and hardwood pack ticket you'll ever see. These worked examples show the calculation in the context you'll actually meet it.

Buying a Hardwood Pack for a Table

A weekend woodworker orders a rough-sawn walnut pack: 12 boards, 4/4 × 8" nominal × 8 feet. Each board is (1 × 8 × 8) ÷ 12 = 5.33 BF. Twelve boards = 64 BF. At $9/BF the material bill is $576 before shipping. If the dealer surfaces the wood to S2S, the finished thickness drops to 13/16" but the invoice still reads 64 BF — you pay for the rough volume, not what's left after planing.

Framing a Deck

A 12 × 16 ft deck needs 30 pieces of 2×8 × 12 ft joists. Each joist is (2 × 8 × 12) ÷ 12 = 16 BF. Total = 480 BF. Softwood construction lumber is often quoted by the piece rather than by BF, so the calculator is most useful here for comparing pallet-pricing offers or estimating dumpster weight (softwood ≈ 3 lb per BF at kiln-dried moisture).

Estimating Yield from a Backyard Log

A landowner has a felled red oak: 16-inch small-end diameter × 12 feet long. International ¼-inch estimates ~135 BF of sawn output. Doyle estimates 108 BF (undervalues small logs). A local band-mill sawyer quotes $0.55 per Doyle BF; on paper the cut costs $59, but on an International basis the true yield is closer to 135 BF — a 25% overrun that stays with the log owner.

Buying by MBF — Sawmill Wholesale

MBF is "thousand board feet" (M = Roman numeral for 1,000, not the metric mega-). A pallet quoted at "1.2 MBF" is 1,200 board feet. Sawmills and wholesalers price hardwood by the MBF because per-BF numbers get impractical at industrial volumes. Divide any $/MBF number by 1,000 to compare with retail $/BF quotes.

Converting Between BF and Linear Feet

A hardwood board's BF-per-linear-foot depends on its cross-section. A 4/4 × 6" plank yields 0.5 BF per foot; a 4/4 × 12" plank yields 1.0 BF per foot. Use the formula BF/LF = (T × W) ÷ 12 to convert either direction. For dimensional softwood, use the nominal size (2×6 → 1.0 BF/LF).

Board Foot Conversions and Equivalents

The three conversions that come up on almost every job:

BF ↔ Linear Feet (LF)

LF = BF ÷ (T × W ÷ 12) — solve for how many running feet you need of a given cross-section. Example: to fit 40 BF of 4/4 × 8" oak into a rack, you need 40 ÷ (1 × 8 ÷ 12) = 60 linear feet of board.

BF ↔ Cubic Feet

1 cubic foot = 12 board feet. A "cord" of firewood (128 ft³) is roughly 1,536 BF of solid wood — though a stacked cord actually contains air gaps and yields closer to 60–90 ft³ of solid volume.

BF ↔ Cubic Meters

1 m³ ≈ 423.78 BF (and inversely, 1 BF ≈ 0.002360 m³). Useful when comparing US quotes with international shipments priced in cubic meters — a shipping container of hardwood at 25 m³ is roughly 10,600 BF.

Square Feet ↔ Board Feet

Sheet goods (plywood, MDF) are priced by the square foot; hardwood by the board foot. To convert between them, multiply the sq-ft area by the thickness in inches, then divide by 12. A 4 × 8 sheet of ¾" plywood = 32 sq ft × 0.75 ÷ 12 = 2 BF equivalent — but the sheet is still sold by the sheet, not the board foot.

Frequently Asked Questions

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.

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