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Board Foot Calculator

By Nick Major · Founder, Calculator Campus Last updated May 4, 2026

The board foot calculator helps woodworkers, sawyers, and lumber buyers measure lumber volume and price an order in seconds. In milled-lumber mode, enter thickness, width, length, quantity, and an optional price per board foot to get board feet per piece, total BF, and estimated cost. In standing-log mode, enter small-end diameter and length to estimate Doyle Rule board-foot yield. A board foot is a volume unit equal to 144 cubic inches — a piece 1 inch thick, 12 inches wide, and 12 inches long.

Inputs

Adjust your numbers

Results update as you type.

Use milled lumber for boards; use Doyle log rule for raw-log yield estimates.
How many matching boards or logs you are tallying.
Board thickness. Hardwood sellers often quote rough thickness as 4/4 = 1 inch, 5/4 = 1.25 inches, and so on.
Board face width before applying the board-foot formula.
Small-end diameter inside bark for Doyle Rule log scaling.
Board or log length. Choose the unit below.
Optional. Multiplies the calculated total board feet by a quoted $/BF rate.

Assumptions

  • Milled-lumber mode uses thickness and width converted to inches and length converted to feet, then applies (T × W × L) ÷ 12.
  • One board foot equals 144 cubic inches: 1 inch thick by 12 inches wide by 12 inches long.
  • Doyle mode uses diameter inside bark at the small end of the log and clamps logs 4 inches or smaller to zero board feet.
  • Price per board foot is optional and multiplies only the calculated total board feet.
Results

Live answer

Total board feet —
Board feet per piece —
Estimated total cost —
Calculation basis —
How it works

Assumptions and detail

Adds mixed-unit board-foot math, optional cost roll-up, and a Doyle Rule branch for users estimating standing-log yield from small-end diameter.

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How the math works

The formulas and what each part means

Board feet per piece (milled lumber)

Multiply thickness by width by length, all measured in inches. Divide the result by 144 to convert cubic inches to board feet.

Board Feet = (Thickness × Width × Length) / 144

Standard board-foot definition: 1 board foot = 144 cubic inches. Inputs are converted to inches before applying the formula. If length is supplied in feet, the equivalent form BF = (T_in * W_in * L_ft) / 12 is used internally and yields the same result.

Total board feet

Multiply the per-piece board-foot value by the number of pieces to find the total board feet for the full order.

Total Board Feet = Number of Pieces × Board Feet

Multiplies the per-piece board-foot value by the number of pieces tallied.

Total cost

Multiply total board feet by the price per board foot to find the full cost of the order.

Total Cost = Total Board Feet × Price per Board Foot

Optional output. Skipped when no price per board foot is entered.

Doyle Rule (standing log mode)

Subtract 4 from the log diameter, divide by 4, then square the result. Multiply by the log length in feet to estimate usable lumber yield.

Log Board Feet = ((Diameter − 4) / 4)² × Length in Feet

Estimates usable lumber yield from a raw log measured at the small end. The (D-4) term is the historical slab/edging allowance baked into the rule. Doyle is known to under-estimate small logs and over-estimate large ones; it is the most common scaling rule in the U.S. South and Midwest.

Methodology

How the answer is computed

The calculator starts by converting your inputs into board feet for one piece using nominal thickness in inches, width in inches, and length in feet. It then multiplies that per-board result by your quantity to get total BF across the whole order. Finally, it multiplies total BF by your price per board foot to produce a total cost. For log estimates, the tool applies the Doyle log rule, which uses the small-end diameter and log length to predict how much usable lumber a log will yield.

Worked examples

See the math step by step

Pricing white oak boards for a dining table top

Sarah is shopping for white oak at the lumberyard to build a dining table top. She picks out 12 boards, each measuring 1.25 inches thick (5/4 stock), 10 inches wide, and 8 feet long. The board foot formula multiplies all three dimensions in inches and divides by 144, so 8 feet first becomes 96 inches. Each board comes to 1.25 × 10 × 96 ÷ 144 = 8.33 board feet. The full set of 12 boards totals 100 board feet. White oak at this yard costs $5.50 per board foot, so the whole order runs 100 × $5.50 = $550.00.

Estimating cedar decking for a backyard deck

Marcus is building a backyard deck in Portland and needs 20 cedar boards. He's using 2×6 lumber, which actually measures 1.5 inches thick and 5.5 inches wide, cut to 12-foot lengths. Running the board foot formula on one board: 1.5 × 5.5 × 144 ÷ 144 = 8.25 board feet. Twenty boards at that rate give 20 × 8.25 = 165 board feet total. Cedar decking runs $4.25 per board foot at the local yard. The lumber bill comes to 165 × $4.25 = $701.25.

When to use this calculator

Use the board foot calculator when buying hardwood at a lumber yard that sells by BF rather than by the piece or linear foot. A cabinetmaker ordering walnut for a kitchen build, for example, needs to know exactly how many board feet to request before calling a supplier. The calculator also helps when pricing a custom furniture quote from a quoted $/BF rate. Use the Doyle mode only for a rough standing-log or saw-log yield estimate; it is not a mill tally and will not capture grade, defects, taper, or local scaling rules.

Nominal vs. Actual Thickness

Lumber is sold by its nominal thickness, which is the size before the mill planes it smooth. A board called 5/4 stock measures 1.25 inches in name but may surface down to about 1.0 inch once it is dried and planed. The board foot calculator uses the nominal thickness because that is how lumber yards price and invoice their wood. Knowing this distinction keeps your BF counts and cost estimates accurate from the start.

Rough-Sawn vs. Surfaced Lumber

Rough-sawn lumber comes straight from the saw and keeps close to its nominal dimensions. Surfaced lumber has been planed on one or both faces, so the actual thickness is smaller. Both types are priced by the board foot using nominal size. When you shop for surfaced lumber, the BF price already accounts for the material removed during surfacing, so you do not need to adjust your inputs.

Assumptions

What we assume

  • The formula takes each entered dimension as exact and applies no rounding or mill-tolerance correction.
  • The result assumes every piece in the batch has the same thickness, width, and length.
  • The formula applies one price per board foot and does not vary cost by piece or quantity.
  • Inputs are treated as nominal inches for thickness and width, not the smaller actual sizes of dressed lumber.
  • Doyle log mode clamps logs 4 inches or smaller at the small end to zero board feet because of the rule's 4-inch allowance.
Limitations

What this skips

  • Does not subtract kerf or planing waste — actual usable wood always falls short of the stated board feet.
  • Excludes defects such as knots, splits, and wane that cut into the usable portion of each piece.
  • Does not apply to log scaling, where taper and diameter change along the length.
  • Ignores lumber grade — a Select board and a No. 3 board have different prices at the yard.
  • Excludes secondary costs like delivery, kiln drying, and surfacing that change the final price.
Common mistakes

What people miss

  • You enter board length in inches instead of feet, which inflates the result by a factor of 12.
  • Mixing nominal size with actual dressed size gives a count that is too high by 10 to 20 percent.
  • Forgetting to enter the number of pieces means the total reflects only one board, not the full stack.
  • You round a 1.5-inch board down to 1 inch and lose a third of its volume in the process.
  • You enter a price per lineal foot instead of per board foot, which gives a wrong total cost.
References

References

  1. Board foot calculator — procore.com

    procore.com · accessed 2026-05-04

  2. How to calculate board footage — hardwoodstore.com

    hardwoodstore.com · accessed 2026-05-04

  3. What is a board foot — woodmizer.com

    woodmizer.com · accessed 2026-05-04

  4. Bfcalc — hardwoodind.com

    hardwoodind.com · accessed 2026-05-04

  5. What is a board foot and how do you calculate it — finewoodworking.com

    finewoodworking.com · accessed 2026-05-04

  6. Lumber lingo understanding board feet — jwlumber.com

    jwlumber.com · accessed 2026-05-04

  7. Units of Measure — mrslumber.com

    mrslumber.com · accessed 2026-05-04

  8. Log board foot calculator — catalesawmill.com

    catalesawmill.com · accessed 2026-05-04

  9. Board foot calculator — livingknotlumber.com

    livingknotlumber.com · accessed 2026-05-04

Frequently asked questions

What is the formula for converting thickness, width, and length into board feet?
Multiply thickness in inches by width in inches, then multiply by length in feet, and divide by 12. If you measure length in inches instead, divide by 144 to get the same result. A 1-inch-thick, 12-inch-wide, 12-inch-long board equals exactly 1 board foot.
How do I calculate board feet for my woodworking project?
Use the nominal dimensions of your lumber — the rough-sawn size — not the smaller finished size. Add up all boards to find the total board feet for your project.
Should I round up or down when calculating board feet for purchasing?
Always round up when buying lumber, since mills sell in whole or half-foot increments. Board feet measure volume, not surface area, so a thicker board in the same length costs more lumber. Rounding up by a small margin beats running short mid-project.
How much waste should I add to my board footage estimate?
Add 10 to 20 percent to your total board footage to cover cuts, defects, and mistakes. When your project uses boards of different sizes, calculate each one separately. Add all the results together before applying the waste buffer.
How do I determine the cost of lumber based on board feet?
Find the price per board foot from your lumber dealer, then multiply it by your total board footage. Prices vary by species, grade, and log-scaling method — the Doyle log rule works well for large logs but underestimates yield from small ones. Small-log lumber often costs more per board foot because of this.

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