Board Feet Calculator

If you are building a workbench out of ten 2×6 boards, each 8 feet long, you are not buying "ten boards" as far as the lumberyard is concerned - you are buying 80 board feet of lumber. At $4.50 per board foot that is $360 in material before tax, and you should order about 88 board feet to leave a 10% cushion for cuts and defects. This board feet calculator turns the dimensions on your cut list into the exact board-foot total and dollar figure the supplier will charge, so you walk in knowing the number instead of guessing at the counter.

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.

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 $4.50 per board foot: 80 × $4.50 = $360.00.
• With a 10% waste cushion: about 88 board feet, or roughly $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.

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, across the narrow face. For hardwood, use the rough thickness you are charged for (a 4/4 board counts as 1 inch).
2. Width in inches, across the wide face. On rough stock, measure the widest usable point.
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.

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 the moment you press Calculate board feet: 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 errors. Surfaced softwood lumber is named by its nominal size but is actually smaller: a "2×4" measures about 1.5 × 3.5 inches, and a "1×6" is about 0.75 × 5.5 inches. Rough hardwood, by contrast, is usually figured at its full rough thickness. Always enter the dimensions the seller actually charges for - using nominal sizes on surfaced softwood will overstate your board feet and your budget.

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 (the most common dimension stock)
• 5/4 = 1.25 inches (popular for stair treads and 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 $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.
• Shop shelving in pine: twelve 1×12 boards at 8 ft = (1 × 12 × 8) ÷ 12 × 12 = 96 board feet, roughly 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) before surfacing; larger than the actual finished size.
• 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 - 8/4 stock costs roughly twice as much per board as 4/4 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 (15-20% 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.

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 dimensions you are actually charged for (rough for hardwood, actual for surfaced softwood).
• 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).