Board Feet Calculator

A board feet calculator finds lumber volume from BF = (thickness in inches × width in inches × length in feet) ÷ 12, then multiplies by quantity. Ten 2×6 boards 8 feet long equal (2 × 6 × 8) ÷ 12 × 10 = 80 board feet: $360 at an example price of $4.50 per board foot, or $396 once you add a 10% waste cushion.

Board feet measure wood volume, so this tool applies whenever lumber is priced by the board foot. For the rest of a build, a different calculator fits: the Concrete Calculator handles footings and slabs in cubic yards, the Paint Calculator covers walls in gallons, and the Roofing Calculator and Roof Pitch Calculator size and slope a roof in squares. Reach for this board feet calculator only when you are buying wood by volume.

What is a board foot?

A board foot (abbreviated BF) is a unit of volume, not length. One board foot equals 144 cubic inches: the amount of wood in a piece 1 inch thick, 12 inches wide and 12 inches long. Because it measures volume, very different-looking boards can hold the same number of board feet: a 1×12 one foot long and a 2×6 one foot long are both exactly 1 board foot. Most hardwood is sold by the board foot, which is why knowing this number matters for pricing. In practice the count uses the nominal thickness and width and the actual length, and lumber under 1 inch nominal thickness counts as 1 inch (USDA Wood Handbook).

The board foot formula

The standard formula expresses thickness and width in inches but length in feet, then divides by 12 to keep the units consistent:

The divide-by-12 converts the foot of length into inches so all three dimensions are effectively measured the same way and the result lands in standard 144-cubic-inch board feet. Multiply by the number of boards to get your project total, then add a waste allowance before you buy.

A worked example

Say you need lumber that is 2 inches thick, 6 inches wide and 8 feet long, and you need 10 boards. Plug it in:

• Per board: (2 × 6 × 8) ÷ 12 = 8 board feet.
• Total: 8 × 10 boards = 80 board feet.
• At an example price of $4.50 per board foot: 80 × $4.50 = $360.00.
• With a 10% waste cushion: 88 board feet, or $396.00.

That last line is the number to budget: the exact figure is what the wood becomes, but the cushion is what you actually buy. These are the calculator's default inputs; enter 4.50 in the price field to see the same cost. Here is the same example broken into steps:

How to measure your lumber correctly

Accurate board feet start with the right dimensions. Measure in the order the formula expects:

1. Thickness in inches. For surfaced softwood use the nominal size (a 2x4 is 2 inches); for hardwood use the rough thickness in quarters (a 4/4 board counts as 1 inch). Anything under 1 inch nominal counts as 1 inch.
2. Width in inches: the nominal width for surfaced softwood (a 2x6 is 6 inches); measure rough hardwood across the face.
3. Length in feet. If a board is 90 inches long, divide by 12 to get 7.5 feet before entering it.
4. Quantity: the number of identical boards of that size.

If your cut list mixes sizes, run each size through the calculator separately and add the totals together.

Board feet chart by lumber size and length

How many board feet is a 2×4 or a 4/4 board? This chart gives the board feet in one board at common sizes and lengths, computed with BF = (T × W × L) ÷ 12. Softwood rows use the nominal size, as the lumber standard requires; hardwood rows use rough thickness. Multiply the figure by your quantity for the order total.

How to use this calculator

Enter the thickness and width in inches, the length in feet, and how many boards you need. The result updates as you type: read the big total at the top, check the per-board figure, and note the suggested order with a 10% waste allowance. If you add a price per board foot from your supplier, the calculator also shows cost per board and the total cost both at the exact figure and with the waste cushion built in.

Nominal vs. actual dimensions

This is the single biggest source of board-foot confusion. Surfaced softwood lumber is named by its nominal size but is dressed smaller: the American Softwood Lumber Standard (PS 20) dresses a 2×4 to 1-1/2 × 3-1/2 inches and a 1×6 to 3/4 × 5-1/2 inches. The board foot, however, is defined on the nominal size: PS 20 multiplies the nominal thickness in inches by the nominal width in feet and the length in feet, and the USDA Wood Handbook adds that lumber under 1 inch nominal thickness is counted as 1 inch. So an 8-foot 2×4 is 5.33 board feet on a lumber tally even though it holds only 3.5 board feet of wood. Rough hardwood is tallied at its rough thickness in quarters (4/4 = 1 inch). Dressed sizes come into play only when lumber is sold by cubic measure.

Reading hardwood thickness: 4/4, 5/4, 8/4

Hardwood thickness is quoted in quarter-inches. The numbers translate directly to the thickness field:

• 4/4 = 1 inch
• 5/4 = 1.25 inches (stair treads, tabletops)
• 6/4 = 1.5 inches
• 8/4 = 2 inches (legs, thick benchtops)

These reflect rough thickness before planing, which is what you pay for, so enter them as-is.

Who this calculator is for

Anyone who buys lumber by volume or wants to compare lumber prices benefits from a quick board-foot total:

• Woodworkers and furniture makers pricing hardwood for a project from a cut list.
• DIY builders estimating framing, decking, fencing or shelving material.
• Contractors and carpenters turning a takeoff into a material order and budget.
• Sawmill and lumberyard customers double-checking the figure on a quote.
• Hobbyists comparing the real cost of two species priced per board foot.

Three quick scenarios

The same formula scales from a single shelf to a full pallet:

• One walnut tabletop board: 8/4 (2 in) × 10 in × 6 ft = (2 × 10 × 6) ÷ 12 = 10 board feet. At an example price of $12/BF that is $120 for one slab.
• A small deck frame: twenty 2×6 boards at 12 ft each = (2 × 6 × 12) ÷ 12 × 20 = 240 board feet. Add 10% and order about 264 BF. To size the joists, beams and decking for the whole structure, pair this with the Deck Calculator.
• Shop shelving in pine: twelve 1×12 boards at 8 ft = (1 × 12 × 8) ÷ 12 × 12 = 96 board feet, about 106 BF with the waste cushion.

Key lumber terms explained

• Board foot (BF): a volume of 144 cubic inches; the standard unit for pricing hardwood.
• Linear (running) foot: a measure of length only, used for fixed-cross-section dimensional lumber.
• Nominal size: the named size of a board (2×4), larger than the dressed size; board feet are figured on it.
• Waste factor: the extra percentage you buy to cover saw kerf, planing loss, defects and mistakes; typically 10%, more for figured wood.
• Cubic yard: a volume of 27 cubic feet used for bulk materials like concrete, gravel and mulch: a different unit than board feet, but the same idea of pricing by volume.
• Kerf: the width of material a saw blade removes with each cut, which adds up across many cuts.

What changes the result the most

Adjust the inputs and a few drivers stand out:

• Thickness: doubling thickness doubles the board feet, so at the same price per board foot an 8/4 board costs twice as much as a 4/4 board of the same face size.
• Width: wider boards carry proportionally more volume; a 1×12 holds twice the board feet of a 1×6 at the same length.
• Quantity: the multiplier that scales a single board up to the whole order.
• Price per board foot: the lever that turns volume into dollars; species and grade swing this the most.
• Waste factor: the 10% cushion is the difference between the wood you use and the wood you buy.

Tips for ordering lumber

• Always order about 10% extra (15 to 20% for figured or highly detailed work) so you can cut around knots and defects.
• Buy long where you can: longer boards yield fewer offcuts and more usable lengths per board foot.
• Hand the supplier a cut list: board-foot totals per size make pricing fast and accurate.
• Compare species by board foot, not by board: a cheap-looking board can be expensive once you factor in its volume.
• Account for planing: rough stock loses thickness when surfaced, so start a touch thicker than the finished part needs.

How board-foot pricing varies by species and grade

The board foot is just a unit of volume; what makes one slab cost ten times another is the price per board foot, and that swings enormously with species, grade, thickness and width. Quartersawn stock, wide boards and figured cuts such as "curly" or "birdseye" usually cost more per board foot than plain-sawn boards of the same species. Prices change with the market, so compare current quotes from local suppliers rather than published averages.

Grade matters just as much as species. Hardwood is sorted by the National Hardwood Lumber Association (NHLA) into grades such as FAS (First and Seconds, the cleanest), Select, and the lower Common grades, based on the size and number of clear, defect-free cuttings you can get out of each board. A lower grade is cheaper per board foot but yields less usable wood, so the effective cost can be similar once you account for the extra waste. When you compare two quotes, divide each total by the usable board feet you expect to recover, not just the gross board feet on the tag.

Lumber cost by board feet and price per board foot

To calculate board foot price, multiply total board feet by the supplier's price per board foot. This table shows the total material cost at a range of prices; enter your own figure in the calculator for an exact number. Prices below are illustrative dollar amounts only, not current market rates.

Estimating lumber weight from board feet

Board feet also give you a quick handle on weight, which matters for transport, floor loading and whether your project fits in the back of a sedan or needs a truck. Wood weight is usually expressed in pounds per cubic foot at a given moisture content, and one board foot is one-twelfth of a cubic foot. So a rough rule is: multiply your board feet by the species' density (pounds per cubic foot) and divide by 12 to get pounds.

For example, the USDA Wood Handbook works out white ash at 12% moisture content to 42.2 pounds per cubic foot, so 80 board feet of rough 4/4 ash weighs about (80 × 42.2) ÷ 12 = 281 pounds, a meaningful load. Because board feet are counted on the nominal size, use the dressed size for surfaced lumber: a dressed 2×6 holds only 69% of its nominal volume (1.5 × 5.5 vs. 2 × 6 inches), so scale the result down accordingly. Wet, freshly sawn lumber weighs more than dried stock because of the water it holds; the Wood Handbook's density tables give values by species and moisture content.

Board feet vs. sheet goods and dimensional lumber

Not every wood product is priced by the board foot, and mixing units is a common budgeting trap. Plywood, MDF and OSB are sheet goods sold by the panel (typically 4×8 feet) or by the square foot of face area, not by volume, so a board-foot figure does not apply to them. Dimensional softwood (the 2×4s and 2×6s at a home center) is frequently sold by the piece or by the linear foot for a fixed cross-section, even though you can still convert it to board feet for comparison. Hardwood from a specialty supplier or sawmill is the product most reliably sold by the board foot.

The practical takeaway: use this board feet calculator for anything priced by volume (mostly rough and surfaced hardwood and bulk softwood) and switch to an area-based tool for panels and coverings. To lay out a floor or wall in square feet before you shop, the Square Footage Calculator and Flooring Calculator are the right fit, and for drywall the Drywall Calculator works in sheets rather than board feet.

Board feet in metric units

Outside North America, lumber is sold by the cubic meter instead. Since an inch is exactly 2.54 cm, one board foot (144 cubic inches) equals 2,359.7 cm³, about 0.00236 m³ or 2.36 liters, and one cubic meter holds about 423.8 board feet. If you are comparing a European price list or working from metric plans, the German-language board feet calculator on Werkbank converts a board-foot tally straight into cubic meters and liters.

Limitations and assumptions

This is a planning estimate, not a guaranteed material count. Keep these in mind:

• It calculates one board size at a time; add separate sizes together for a mixed order.
• The 10% waste allowance is a default: increase it for difficult layouts and decrease it only when you are confident in tight, simple cuts.
• It assumes you enter the tally dimensions: nominal for surfaced softwood, rough quarter-inch thickness for hardwood; lumber under 1 inch is counted as 1 inch.
• It does not include sales tax, delivery, or per-piece minimums some suppliers apply.
• Real-world yield depends on defects, grain, and your cutting strategy, which no formula can predict exactly.

Related materials and calculators

Board feet answers "how much lumber and what will it cost?" For other materials, a sister tool fits better:

• For slabs, footings and columns, use the Concrete Calculator (cubic yards).
• To measure a room or area first, use the Square Footage Calculator.
• For driveways and base material, use the Gravel Calculator (tons or cubic yards).
• For garden beds, use the Mulch Calculator (cubic yards or bags).
• To convert any dimensions to bulk volume, use the Cubic Yard Calculator.
• To estimate wall coverage, use the Paint Calculator (gallons).
• Building outdoors? The Deck Calculator and Fence Calculator size joists, decking and pickets, while the Stair Calculator lays out rise and run.

Sources

• NIST: Voluntary Product Standard PS 20-20, American Softwood Lumber Standard (2.2 board measure on nominal thickness and width; Table 3 dressed sizes).
• USDA Forest Service, Forest Products Laboratory: Wood Handbook: Wood as an Engineering Material (FPL-GTR-190) (glossary definition of the board foot, density and moisture content).
• National Hardwood Lumber Association (NHLA): Hardwood lumber grading rules (FAS, Select and Common grades).