How Is Wood Calculated? Board Feet, Cords, and Log Scale Explained
Wood is calculated differently depending on what you’re buying: hardwood lumber is priced by the board foot, dimensional softwood (2x4s, 2x6s) is priced by the linear foot, firewood is sold by the cord, and standing timber is measured by log volume — and these methods aren’t interchangeable. Using the wrong one is the most common reason people get a cost estimate wrong before a project even starts.
Board Feet: The Hardwood Lumber Standard
For Nominal-vs-Actual Measurements
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NEIKO 01407A Digital Caliper, 6 Inch – $27.99 The tool that actually catches the difference between a board’s nominal size (what it’s sold as) and its real, planed dimension — the single biggest source of board-foot miscalculation.
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Stanley FatMax Tape Measure, 25 ft – $21.99 For the length measurement in a board-foot calculation, plus stacking a cord of firewood to the actual 4x4x8’ standard. View on Amazon |
General Tools MMD4E Pin-Type Wood Moisture Meter – $37.70 Moisture content shifts a board’s actual dimensions — check it before a precise calculation matters (kiln-dried vs. air-dried stock especially). View on Amazon |
Digital Hanging Luggage Scale, 110 lb – $39.99 Weight-based estimates are a real cross-check for board footage when you can’t measure every piece in a mixed pile. View on Amazon |
One board foot equals a piece of wood 1″ thick, 12″ wide, and 12″ long (144 cubic inches). The formula:
Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12
The detail almost every guide skips: hardwood lumber is priced using nominal thickness in quarters — 4/4 (one inch), 5/4, 6/4, 8/4 — even after the board has been surfaced and is actually thinner. A “4/4” board planed on two faces (S2S) is typically about 13/16″ thick in reality, but you’re still billed board footage based on the full 1″ nominal figure. This isn’t a mistake or a rip-off — it’s the accepted industry convention — but it means measuring your actual board with a caliper and plugging that number into the formula will undercount what you’re actually paying for. For pricing purposes, always use the nominal quarter-thickness the lumberyard sold it as, not your caliper reading.
Why Big-Box 2x4s Don’t Use Board Feet at the Register
Dimensional softwood lumber (2×4, 2×6, 2×10, etc.) is sold by the linear/running foot at most home centers, not by the board foot — the price tag is per 8-foot or 10-foot piece, full stop. The “2×4” nominal size is also famously not 2″ by 4″ in reality; it’s surfaced down to about 1.5″ by 3.5″. If you do need board footage for dimensional lumber (for a material takeoff, for example), the same formula applies, but use the actual finished size, not the nominal name — this is the reverse of the hardwood convention above, which is exactly why the two get confused.
Cords vs. Face Cords: A Very Common Mix-Up
A full cord is a stack measuring 4’ × 4’ × 8’ — exactly 128 cubic feet, regardless of how long the individual pieces are cut. A “face cord” (also called a rick) is not a standardized fraction of a cord — it’s a stack 4’ high by 8’ long, but only as deep as the firewood pieces are cut, which varies by seller. If the pieces are cut to a common 16″ length, a face cord works out to roughly 1/3 of a full cord (about 42-43 cubic feet), but with 12″ pieces it’s closer to 1/4, and with 24″ pieces closer to 2/3. This is exactly why “face cord” prices vary so much between sellers who don’t specify their cut length — always ask for the piece length before comparing a face-cord price to a full-cord price. See our full rick-to-cord breakdown for the exact ratios at common cut lengths.
Standing Timber: Why Loggers Use a Different Number Entirely
Board feet and cords measure cut lumber or stacked firewood. Standing or felled logs are measured with a log rule instead — and there isn’t just one. The Doyle, Scribner, and International 1/4-inch rules all estimate the board feet a given log will yield, and they routinely disagree with each other by 10-30% on the same log, because each rule makes different assumptions about saw kerf and slab waste. Doyle tends to underestimate yield on smaller logs; International 1/4″ is generally considered the most accurate modern standard. If you’re buying or selling standing timber, confirm which rule a quoted price is based on — comparing a Doyle-based quote to a Scribner-based one as if they were the same measurement is a common and costly mistake. For a worked example on a specific log size, see how many board feet are in an 8-foot log.
Frequently Asked Questions About How Wood Is Calculated
What is the formula for board feet?
Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12. For hardwood, use the nominal quarter-thickness (4/4, 5/4, etc.) it was sold as, not the actual measured thickness after surfacing.
Why is my board thinner than what I paid for?
Hardwood lumber is priced by nominal thickness (in quarters) before surfacing, not the finished thickness. A 4/4 board surfaced on two faces typically finishes around 13/16″ even though you were billed for a full 1″. This is standard industry practice, not a measurement error.
Is a face cord the same as a half or quarter cord?
Not reliably. A face cord’s volume depends on how long the individual pieces are cut, since it’s only defined as 4’ high by 8’ long — the depth varies. With common 16″ pieces it’s close to 1/3 of a full cord, but it isn’t a fixed, standardized fraction the way “half cord” is.
Why do timber quotes vary so much for the same log?
Because different log scaling rules (Doyle, Scribner, International 1/4-inch) estimate board-foot yield differently for the same log, sometimes by 10-30%. Always confirm which rule a quote is based on before comparing prices between buyers.
