How do you calculate board feet in a log?

Log board footage is estimated with a log rule based on the small-end diameter (inside the bark) and length of the log, not measured directly like a sawn board. The three US log rules are Doyle (an exact formula: BF = ((D - 4) / 4)^2 x L), Scribner Decimal C (a diagram-based lookup table), and International 1/4-inch (a formula with a built-in kerf allowance, generally considered the most accurate). Because the rules use different assumptions about saw kerf and slabbing loss, the same log can scale to noticeably different board-foot totals depending on which rule is used — always confirm which rule a quoted log price is based on.

How do you measure a board foot?

One board foot is a volume of 144 cubic inches — the equivalent of a board 12 inches long, 12 inches wide, and 1 inch thick. For any board, multiply thickness (inches) x width (inches) x length (feet) and divide by 12, or, if length is also in inches, multiply all three dimensions in inches and divide by 144. Use actual (surfaced) dimensions for a true count of what you are getting, or nominal (trade) dimensions if you are pricing rough-sawn stock.

How many board feet are in a 2x4?

It depends on the length. A nominal 2x4 measures 1.5" x 3.5" actual, so an 8-foot 2x4 is 8 x 3.5 x 1.5 / 12 = 3.5 board feet, a 10-foot 2x4 is 4.375 board feet, and a 12-foot 2x4 is 5.25 board feet. If you calculate using the full nominal 2" x 4" size instead of the actual 1.5" x 3.5" surfaced size, an 8-foot piece comes to 5.33 board feet — a meaningfully higher and incorrect number for surfaced lumber, which is why the nominal-vs-actual toggle matters.

What is the difference between a board foot and a linear foot?

A linear foot measures length only, regardless of the board's width or thickness — a 10-foot 2x4 and a 10-foot 2x12 are both "10 linear feet," even though the 2x12 contains far more wood. A board foot measures volume (144 cubic inches), so it accounts for width and thickness as well as length. Two boards can have the same linear footage but very different board footage, which is why lumber that varies in width or thickness is priced and quoted in board feet, not linear feet.

What is board foot insulation?

Spray foam insulation is also measured and quoted in board feet, using the same 144-cubic-inch definition as lumber: one board foot of foam covers 12 square feet of surface at 1 inch of thickness (or 1 square foot at 12 inches thick). A two-component spray foam kit is typically rated in total board feet of coverage at a specified thickness, so contractors convert wall or ceiling area and desired foam thickness into board feet to size the right kit — the unit is identical, but the material and the surface-coverage framing are different from lumber board footage.

How much does a board foot of oak weigh?

A board foot of oak weighs roughly 3.08 to 4.67 pounds depending on species (red vs. white oak), moisture content, and density variation within the tree, averaging around 3.875 pounds per board foot for kiln-dried stock at typical moisture content. Weight matters for shipping estimates and for gauging how "green" (wet) a board still is, since air-dried or unseasoned oak can weigh noticeably more than the kiln-dried average until it reaches equilibrium moisture content.

How many board feet are in 320 square feet?

Board feet and square feet are not directly convertible without a thickness, because square feet measures only area while board feet measures volume. At 1 inch of thickness (4/4 nominal), 320 square feet of surface equals 320 board feet, since 1 board foot is exactly 1 square foot at 1 inch thick. At 2 inches thick (8/4), 320 square feet would be 640 board feet; at 3/4 inch thick (typical surfaced 1-inch nominal stock), it would be 240 board feet. Always multiply the square footage by the thickness in inches to get board feet.

What is a lumber calculator and how is this one different from a single-board tool?

A lumber calculator converts board dimensions and quantity into total board footage and cost. Most online lumber calculators handle only one board size at a time, forcing you to re-run the calculation and add the results manually for a real project with mixed sizes. This calculator's cut-list mode lets you add unlimited rows of different thicknesses, widths, lengths, and quantities — mixing 2x4s, 2x6s, and hardwood boards in a single list — and totals the board footage, waste allowance, and cost for the whole list at once.

Is there a log board feet calculator that compares log rules?

Yes — this calculator's log mode lets you pick Doyle, Scribner (Decimal C), or International 1/4-inch, enter the small-end diameter and length, and get the board-foot estimate under that rule instantly, so you can re-run the same log under a different rule to see how much the estimate changes before accepting or countering a quoted price.

How do I use a price-per-board-foot calculator to get a total cost?

Enter your board (or cut-list) dimensions and quantities to get the total board footage, then enter a price per board foot in the price field. The calculator multiplies your total board footage — including any waste allowance you set — by that price to give you an estimated total cost instantly, and it also supports pricing per piece or per linear foot if that is how your supplier quotes.

How do I use this as a lumber cost calculator for a whole project?

Build your full cut list first — every board size and quantity your project needs, in nominal or actual dimensions — add a waste allowance to cover cutting losses and defects (10% is a common starting point for straightforward cuts, higher for complex joinery or figured hardwood), then enter your price per board foot, per piece, or per linear foot. The calculator returns total board footage with waste included and the full estimated project cost in one number, which you can export or print for a quote or purchase order.

What is the difference between the Doyle, Scribner, and International 1/4-inch log rules?

All three estimate the board feet a log will yield from its small-end diameter and length, but they use different formulas and tables and give different answers for the same log. Doyle is the most common US hardwood log rule and tends to undervalue small logs; Scribner (Decimal C) is common in the Pacific Northwest and is read from a diagram-based table; International 1/4-inch adds a 1/4-inch-per-4-foot kerf allowance and is generally considered the most accurate for actual mill yield. Always check which rule a buyer or mill is quoting before comparing prices.

How do I convert board feet to cubic meters?

1 board foot equals 144 cubic inches, which is about 0.002360 cubic meters — so 1 m3 is roughly 424 board feet. This calculator converts your total board footage to m3 and ft3 automatically alongside the BF total.

Board Foot Calculator – Lumber Cut List, Log Scales & Cost

Board Foot Calculator: Cut Lists, Nominal Sizes & Log Scales

A board foot (BF) is the standard unit for measuring lumber volume in the United States and Canada: a piece of wood 12 inches long, 12 inches wide, and 1 inch thick, or 144 cubic inches total. The formula is simple once you know it — length in feet times width in inches times thickness in inches, divided by 12 — but almost every real-world lumber calculation trips people up in the same two places: whether "2x4" means the rough trade name or the smaller size you actually get after milling, and which log rule a seller is quoting when they price a log by the board foot. This calculator is built to handle both, plus the one thing a single-board tool cannot do at all: price out a whole project cut list of different board sizes in one pass.

The US and Canada settled on the board foot in the 19th century because it scales naturally with how lumber is actually sold — by length off a mill run, in whatever width and thickness a customer orders — rather than in fixed sheet or bundle units. Hardwood dealers, framing lumberyards, and log buyers all still think in board feet (or thousand board feet, "MBF," at wholesale), so it remains the number you need whether you are buying a handful of oak boards for a shelf or scaling standing timber before a harvest.

Below is a complete, step-by-step guide: how to calculate board feet by hand with a full worked example, how nominal and actual dimensions differ (with a full 2x4-through-2x12 and 4/4-through-16/4 conversion table), how the Doyle, Scribner, and International ¼-inch log rules can give three different answers for the exact same log, how to convert board feet to cubic meters, cubic feet, and linear feet, realistic 2026 US lumber pricing by species, and buying tips for lumberyards versus big-box stores.

How to Calculate Board Feet: Step-by-Step

The board foot formula is: board feet = (thickness in inches x width in inches x length in feet) / 12. If your length is also in inches rather than feet, use board feet = (thickness x width x length, all in inches) / 144 — the 144 is simply 12 inches x 12 inches, the cross-section of one board foot.

Here is the exact worked example that most lumber calculators (including Omni Calculator's own board foot tool) use to illustrate the formula, reproduced in full so you can check this calculator against it: 5 boards, each 8 feet long, 10 inches wide, and 1.25 inches thick, at a price of $4.15 per board foot.

Convert the thickness and width to a single board's footage: 8 ft x 10 in x 1.25 in / 12 = 8.333 board feet per board.
Multiply by the number of identical boards: 8.333 BF x 5 boards = 41.67 board feet total.
Multiply the total board footage by the price per board foot: 41.67 BF x $4.15/BF = $172.92 total cost.
Add a waste allowance if you are buying rough or budget-grade stock: at a typical 10% allowance, 41.67 BF becomes 45.83 BF, or about $190.21 before tax.

A Second Example: Why a Single-Board Calculator Is Not Enough

Real projects are almost never one board size. A calculator that only handles one thickness, width, and length at a time — which is how Omni Calculator's tool and most competitors work — forces you to run the calculation over and over and add the results up yourself, or worse, tally on paper and risk a mistake. This tool's cut-list mode adds as many rows as you need and totals them automatically. Here is a realistic mixed-size example: framing a small deck or shed wall with 2x4s, 2x6s, and 2x8s.

10 pieces of 2x4 (actual 1.5" x 3.5"), 8 ft long: 8 x 3.5 x 1.5 / 12 = 3.5 BF each x 10 = 35 board feet.
6 pieces of 2x6 (actual 1.5" x 5.5"), 10 ft long: 10 x 5.5 x 1.5 / 12 = 6.875 BF each x 6 = 41.25 board feet.
4 pieces of 2x8 (actual 1.5" x 7.25"), 12 ft long: 12 x 7.25 x 1.5 / 12 = 10.875 BF each x 4 = 43.5 board feet.
Cut list total: 35 + 41.25 + 43.5 = 119.75 board feet.
At $4.15 per board foot, that is 119.75 x $4.15 = $496.96 before any waste allowance or sales tax — a single total pulled from three different board sizes in one pass, something a one-size-at-a-time calculator cannot produce without manual addition.

Nominal vs. Actual Lumber Dimensions

A "2x4" does not measure 2 inches by 4 inches. The nominal size is the rough-sawn size before the board is dried and surfaced on four sides (S4S); the actual size, which is what you take home and what your project actually uses, is smaller. A nominal 2x4 measures 1.5" x 3.5" actual — that is a 25% reduction in width and a 12.5% reduction in thickness, which is why skipping this step is the single most common source of bad estimates. Hardwood lumber uses a different, thickness-only naming system based on quarters of an inch — 4/4 ("four-quarter") is 1 inch of rough thickness, 8/4 is 2 inches, and so on — and hardwood boards are typically sold with random, ungraded widths rather than fixed nominal widths.

Use this calculator's "actual dimensions" toggle to switch between the two: leave it on to find out how much lumber you will really receive and pay for at a store or yard, or turn it off if you are pricing rough-sawn or full-nominal stock, which some sawmills and hardwood suppliers still sell direct.

1x2 nominal -> 0.75" x 1.5" actual
1x3 nominal -> 0.75" x 2.5" actual
1x4 nominal -> 0.75" x 3.5" actual
1x6 nominal -> 0.75" x 5.5" actual
1x8 nominal -> 0.75" x 7.25" actual
1x10 nominal -> 0.75" x 9.25" actual
1x12 nominal -> 0.75" x 11.25" actual
2x4 nominal -> 1.5" x 3.5" actual
2x6 nominal -> 1.5" x 5.5" actual
2x8 nominal -> 1.5" x 7.25" actual
2x10 nominal -> 1.5" x 9.25" actual
2x12 nominal -> 1.5" x 11.25" actual
4x4 nominal -> 3.5" x 3.5" actual
4/4 hardwood -> 1" rough thickness (roughly 13/16" to 7/8" after S2S surfacing)
5/4 hardwood -> 1.25" rough thickness
6/4 hardwood -> 1.5" rough thickness
8/4 hardwood -> 2" rough thickness
10/4 hardwood -> 2.5" rough thickness
12/4 hardwood -> 3" rough thickness
16/4 hardwood -> 4" rough thickness

Log Scaling: Doyle vs. Scribner vs. International 1/4-Inch

When you are buying or selling standing or felled logs rather than milled boards, board footage is estimated with a "log rule" — a formula or table that predicts how much lumber a mill can saw out of a log, given its small-end diameter (inside the bark) and its length. The catch, and a real gap most online calculators (including Omni's) do not cover at all, is that the three log rules in common US use do not agree with each other, sometimes by a wide margin, because each one models saw kerf and slabbing losses differently.

Doyle is the oldest and most widely used rule for hardwood sawlogs east of the Rockies, and it has a simple exact formula: BF = ((D - 4) / 4)^2 x L, where D is small-end diameter in inches and L is length in feet. Doyle systematically undervalues small-diameter logs because its assumed saw kerf and slabbing loss do not scale down with the log — the smaller the log, the more Doyle underestimates actual mill yield. Scribner (Decimal C) is a diagram-based rule, built from actual saw-cut diagrams for logs of each diameter, that is standard in the Pacific Northwest and on much public timber; because it is table-based rather than a clean formula, mills and buyers look it up rather than compute it. International 1/4-inch is a newer rule that adds a specific 1/4-inch-per-4-foot-section kerf allowance and is generally regarded by foresters as the closest of the three to actual mill output, especially for smaller logs, which is why many public agencies specify it for timber sales.

To show how much the three rules can diverge on the same log, take a 20-inch small-end-diameter log, 16 feet long — a size commonly used in forestry extension examples. Doyle gives ((20 - 4) / 4)^2 x 16 = 4^2 x 16 = 256 board feet exactly, by the formula above. Scribner Decimal C, read from the standard published log-scale table for that diameter and length, comes out meaningfully higher, in the neighborhood of 380 board feet. International 1/4-inch lands in between the two, typically cited around 315-320 board feet for a log this size. On the same physical log, Doyle can under-report actual sawn yield by 30% or more compared with Scribner or International 1/4-inch — which is exactly why it matters to ask, and confirm, which rule a quoted log price is based on before you compare offers from two different buyers or mills.

Board Foot Conversions: m3, ft3, and Linear Feet

Because a board foot is a volume unit (144 cubic inches), it converts cleanly to metric and imperial volume units, and — for a fixed board thickness and width — to a simple linear-feet figure as well. This calculator converts your cut-list or log total to m3 and ft3 automatically; the reference figures below let you do a quick sanity check or convert by hand.

1 board foot = 144 cubic inches = 0.002360 m3 (roughly 1 m3 = 424 board feet).
1 board foot = 0.08333 cubic feet (roughly 1 ft3 = 12 board feet).
1 m3 = 35.31 ft3, the standard cubic-meter-to-cubic-foot conversion used to cross-check the two totals.
Linear feet per board foot depends on the board's actual cross-section: for a 2x4 (1.5" x 3.5" actual), 1 board foot = about 2.29 linear feet; for a 1x12 (0.75" x 11.25" actual), 1 board foot = about 1.42 linear feet.
To convert your own board size: linear feet per board foot = 12 / (actual width in inches x actual thickness in inches).

How Lumber Is Actually Priced in the US

Hardwood and softwood framing lumber are priced completely differently in the US trade, and knowing which applies to what you are buying will save you from comparing two numbers that are not actually comparable. Hardwood — oak, maple, walnut, cherry, and similar species sold at specialty hardwood dealers and small mills — is priced per board foot, exactly as this calculator computes it, with the price varying by species, grade (FAS, Select, or #1/#2 Common under National Hardwood Lumber Association grading rules), and whether the stock is kiln-dried or air-dried. Softwood dimension and framing lumber — SPF (spruce-pine-fir), Douglas fir, and southern yellow pine 2x4s, 2x6s, and similar construction-grade stock — is instead priced per MBF (thousand board feet) at the wholesale and mill level, then converted to a per-piece shelf price at retail and big-box stores; the MBF price is also the number reported daily by lumber-futures and price-index services.

Realistic 2026 US retail price ranges by species (per board foot, hardwood, S2S surfaced, kiln-dried unless noted) are useful for sanity-checking a quote, though actual prices swing with regional supply, grade, and current market conditions:

Red oak: roughly $4.00-$6.50 per board foot at a hardwood dealer — this calculator's $4.15 default price sits at the lower end of that typical red oak range.
Hard maple: roughly $5.00-$8.00 per board foot.
Black walnut: roughly $8.00-$14.00 per board foot, and often considerably more for wide, figured, or thick (8/4+) stock.
Cherry: roughly $6.00-$9.50 per board foot.
Framing lumber (SPF/Douglas fir dimension stock): commonly quoted per MBF at roughly $350-$650 per MBF depending on species, grade, and market conditions, which works out to well under $1 per board foot at retail for standard construction-grade 2x4s and 2x6s — a very different price tier from hardwood.

Species, Grading, and Buying Tips

For furniture, cabinetry, and fine woodworking, the most common US hardwoods are red and white oak, hard and soft maple, black walnut, and cherry, each graded under National Hardwood Lumber Association (NHLA) rules — FAS (First and Seconds) being the highest common grade, down through Select and the #1/#2 Common grades used for shorter or narrower cuttings. For framing and general construction, Spruce-Pine-Fir (SPF) and Douglas fir dominate, graded and stamped under standards set or accredited by the American Lumber Standards Committee (ALSC), which is what puts the grade stamp (species group, grade, and moisture content) on every piece of construction-grade dimension lumber you buy.

A specialty hardwood dealer or sawmill will almost always beat a big-box home center on price per board foot, species selection, and thickness options (4/4 through 16/4 and beyond), and will typically sell hardwood by random width and length rather than fixed nominal sizes — you pay for the board footage you actually take, which is exactly what this calculator is built to total up. Big-box stores are convenient for standard framing dimension lumber, common softwood project boards, and small quantities, but carry a narrower hardwood selection at a higher markup per board foot.

Kiln-dried (KD) lumber is dried in a controlled kiln to roughly 6-8% moisture content, is more dimensionally stable, and is the standard choice for furniture and indoor cabinetry; it costs more than air-dried stock. Air-dried (AD) lumber is stacked and dried naturally over months or years to somewhat higher moisture content (commonly 12-20% depending on climate and time), costs less, and is favored by some woodworkers for certain species and color characteristics, but needs to acclimate further indoors before fine work and is less consistent from board to board. Always ask which drying method you are buying, since it affects both price per board foot and how much additional wood movement to plan for.

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Board Foot Calculator