A board foot is 144 cubic inches of wood: a piece 1 inch thick, 12 inches wide and 12 inches long. It is the unit hardwood dealers use to price lumber, and the unit the framing lumber market uses when it quotes prices per thousand board feet (MBF). Once you know the formula, checking a lumber ticket takes seconds, and a math error on an expensive species is easy to catch before you pay. If you would rather let a tool do it, our free board foot calculator runs the same formula.
Editor's note, October 18, 2026: the July version of this article opened with a story about a customer overpaying on a walnut order and quoted hardwood prices by species, framing lumber at $480 per thousand board feet, volume discounts, delivery fees, yard tallying habits and waste percentages. We could not verify those figures or the anecdote, and they have been removed. The formulas and worked examples have been rechecked, and one error was corrected: a surfaced 2x4 carries about 52% more board feet on paper than its actual wood volume, not 34%.
The Board Foot Formula: T x W x L / 12
Board feet = (thickness in inches x width in inches x length in feet) / 12
Thickness and width go in inches, length in feet, and you divide by 12. If you measure the length in inches too, divide by 144 instead. Both versions convert the piece's volume into 144-cubic-inch units.
Why 12? One board foot is 1 inch x 12 inches x 1 foot. With width in inches and length in feet, a 1-inch-thick, 12-inch-wide, 1-foot-long piece gives 1 x 12 x 1 = 12, and dividing by 12 makes it exactly one board foot.
Worked Example 1: A 2x4, 8 Feet Long
Using nominal dimensions:
(2 x 4 x 8) / 12 = 64 / 12 = 5.33 board feet
Framing lumber is usually sold to contractors by the piece or by the thousand board feet. To turn a per-MBF price into a per-board-foot price, divide by 1,000. At the October 16, 2026 lumber futures price of $532.50 per MBF, reported by Trading Economics, that is about $0.53 per board foot, or about $2.84 for the board-foot content of one 2x4x8 (5.33 x $0.5325). That is a wholesale futures benchmark, not a yard price: dealer markup, species, grade, freight and delivery all sit on top. Our lumber prices 2026 contractor's guide explains how futures relate to what you pay.
Worked Example 2: A Thick Hardwood Board
An 8/4 (2-inch rough) board, 7 inches wide, 10 feet long:
(2 x 7 x 10) / 12 = 140 / 12 = 11.67 board feet
At a hypothetical $10 per board foot, a round number used only to show the arithmetic, that one board would be $116.70. The same board in 4/4 stock would be 5.83 board feet and half the cost, which is why getting the thickness right on a thick-stock order matters.
Worked Example 3: A Project Cut List
A dining table in 4/4 stock:
- Top: 8 boards, 1 in x 6 in x 8 ft: (1 x 6 x 8) / 12 = 4 BF each, x 8 = 32 BF
- Aprons: 2 boards, 1 in x 5 in x 6 ft: (1 x 5 x 6) / 12 = 2.5 BF each, x 2 = 5 BF
- Legs: 1 board of 12/4 (3-inch) stock, 4 in x 12 ft: (3 x 4 x 12) / 12 = 12 BF
Total: 32 + 5 + 12 = 49 board feet before waste.
Rough lumber has defects, and cutting parts from random-width boards always leaves offcuts, so you will buy more than your finished tally. How much more depends on grade and the parts you need. As a guide to grade, the USDA Forest Products Laboratory's Wood Handbook (chapter 6) notes that the top hardwood grade, FAS, must allow at least 83-1/3% of a piece's surface measure to be cut into clear face material. Lower grades yield less. As arithmetic: if you allow 20% extra on the 49 BF table, you buy 49 x 1.20 = 58.8, call it 59 board feet. Pick an allowance that fits your grade and cut list, not a rule of thumb.
For multi-item tallies such as a trim package or a deck frame, our lumber calculator handles several sizes and a waste factor at once.
Board Feet Chart for Common Sizes
Every figure below is (nominal thickness x nominal width x length) / 12, rounded to two decimals.
| Nominal size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1x4 | 2.67 BF | 3.33 BF | 4 BF | 5.33 BF |
| 1x6 | 4 BF | 5 BF | 6 BF | 8 BF |
| 2x4 | 5.33 BF | 6.67 BF | 8 BF | 10.67 BF |
| 2x6 | 8 BF | 10 BF | 12 BF | 16 BF |
| 2x8 | 10.67 BF | 13.33 BF | 16 BF | 21.33 BF |
| 2x10 | 13.33 BF | 16.67 BF | 20 BF | 26.67 BF |
| 2x12 | 16 BF | 20 BF | 24 BF | 32 BF |
| 4x4 | 10.67 BF | 13.33 BF | 16 BF | 21.33 BF |
Two shortcuts make mental checks easy:
- A 2x6 is exactly 1 board foot per linear foot (2 x 6 / 12 = 1), so a 2x6 has as many board feet as it has feet of length.
- Any 12-foot piece has board feet equal to thickness times width, because the 12s cancel. A 2x4x12 is 8 BF; a 2x10x12 is 20 BF.
A 4x4 has the same cross-section in nominal inches as a 2x8 (16 square inches), so their columns match.
To convert a whole order: add up the board feet, divide by 1,000 to get MBF, and multiply by the per-MBF price. Fifty 2x4x8s are 50 x 5.33 = 266.7 BF, or 0.267 MBF.
Nominal vs. Actual Dimensions
A surfaced, dry 2x4 measures 1-1/2 by 3-1/2 inches. The Wood Handbook explains that softwood lumber width and thickness are traditionally recorded in nominal dimensions, with actual dimensions somewhat less, and that the American Softwood Lumber Standard (PS 20) sets the actual sizes.
That gap shows up in board feet. A 2x4x8 counts as 5.33 BF on nominal size. Its actual wood volume is (1.5 x 3.5 x 8) / 12 = 42 / 12 = 3.5 board feet. The nominal tally is about 52% higher than the actual volume (5.33 / 3.5 = 1.52); put the other way, the actual volume is about 34% less than the nominal tally.
Nobody is cheating anyone. Prices are set with the convention in mind. But the Wood Handbook's advice to buyers is direct: board measure depends on whether nominal or actual dimensions are used, and that should be clearly spelled out in the order. When you compare a per-board-foot price from one supplier with a per-piece price from another, make sure both are on the same basis.
Hardwood Quarter Sizes and Surfacing
Hardwood thickness is quoted in quarters of an inch of rough thickness: 4/4 is 1 inch rough, 5/4 is 1-1/4 inches, 8/4 is 2 inches, 12/4 is 3 inches. Dealers commonly tally board feet on that quarter (rough) thickness even when they sell the board surfaced, so ask which thickness your ticket uses.
Surfacing removes wood. The Wood Handbook's table of standard hardwood thicknesses lists these surfaced-two-sides (S2S) sizes:
| Rough | Standard S2S thickness |
|---|---|
| 4/4 (1 in) | 13/16 in |
| 5/4 (1-1/4 in) | 1-1/16 in |
| 6/4 (1-1/2 in) | 1-5/16 in |
| 8/4 (2 in) | 1-3/4 in |
| 12/4 (3 in) | 2-3/4 in |
So if your plan calls for a full 1-inch finished part, 4/4 stock will not get you there after surfacing; 5/4 stock will. That is 25% more board feet per board (1.25 / 1), so price it that way.
Hardwood is also usually sold in random widths, and standard hardwood lengths run in 1-foot increments from 4 to 16 feet, per the Wood Handbook. Each board is measured and tallied rather than counted. The National Hardwood Lumber Association's rules govern grading and measurement for most domestic hardwoods; if you buy a lot of it, ask your dealer how they tally width and length, and spot-check a few boards against the ticket with a tape.
Mistakes That Cost Money
Board feet vs. square feet vs. linear feet. A linear foot is length only. A square foot is surface area and ignores thickness. A board foot is volume. On 1-inch stock, board feet and square feet come out the same, which is how people get into the habit of using area. On 8/4 stock the board feet are double the square feet, and an estimate done on area will be half the real number.
Mixing nominal and actual sizes. If you figure board feet on actual sizes but the supplier prices on nominal, your tally will be about a third low on surfaced 2x material. Agree on the basis.
Forgetting the thickness on thick stock. A 12/4 board has three times the board feet of a 4/4 board of the same width and length.
Not allowing for waste. Rough hardwood has knots, checks, wane and end defects, and grade sets how much clear material you can expect. Plan a margin and buy it in one trip so the boards match.
Rounding errors on long lists. Keep two decimals per line and round only the total.
Frequently Asked Questions
How many board feet are in a 2x4x8?
5.33 board feet on nominal dimensions: (2 x 4 x 8) / 12 = 5.33. The actual surfaced piece, 1-1/2 by 3-1/2 inches, contains 3.5 board feet of wood. Softwood lumber is traditionally tallied on nominal size, so confirm the basis with your supplier.
What is the formula for board feet?
Thickness (in) x width (in) x length (ft) / 12. If all three dimensions are in inches, divide by 144. One board foot equals 144 cubic inches.
What is the difference between a board foot and a linear foot?
A linear foot measures length only; a board foot measures volume. A 10-foot 1x4 is 10 linear feet and 3.33 board feet. A 10-foot 2x12 is also 10 linear feet but 20 board feet, six times as much wood.
Why is my 4/4 hardwood board less than 1 inch thick?
4/4 describes the rough thickness. The Wood Handbook lists the standard surfaced-two-sides thickness of 4/4 hardwood as 13/16 inch. If you need a full inch finished, buy 5/4, which surfaces to 1-1/16 inch.
How do I convert board feet to MBF?
Divide by 1,000. 2,500 board feet is 2.5 MBF. To price it, multiply MBF by the per-MBF price; at the October 16, 2026 futures price of $532.50, 2.5 MBF is $1,331.25 before dealer markup, freight and delivery.
How much extra should I order for waste?
It depends on the grade and the cut list. Higher grades yield more clear material: FAS hardwood must allow at least 83-1/3% of its surface measure to be cut into clear face pieces, per the Wood Handbook, and lower grades yield less. Lay out your parts on the boards you expect to buy and add a margin that fits; buying the extra in one order keeps color and grain consistent.
