October 18, 2026
How to Calculate Board Feet
Knowing how to calculate board feet is the difference between quoting a job with confidence and guessing at the lumber pile. Board feet are the trade's common currency: sawmills price logs and rough lumber in board feet, sellers list stock in board feet, and buyers compare prices in board feet — even when the boards in front of them are completely different sizes. One board foot is simply a unit of volume: a piece of wood 1 inch thick, 12 inches wide and 12 inches long, or 144 cubic inches of wood in any shape that adds up to the same volume.
Because it measures volume rather than length or area, the board foot lets a thick walnut slab, a stack of 1×6 pine and a bundle of 2×4 studs all be priced on the same basis. Get the calculation right and you can check any invoice, estimate how much lumber a log should yield, and work out exactly what a custom sawing job should cost before anyone starts a saw.
The Board Foot Formula
The standard formula uses thickness and width in inches and length in feet:
Board feet = (thickness in inches × width in inches × length in feet) ÷ 12
If every measurement is in inches, divide by 144 instead — the two versions are the same calculation, because 144 cubic inches equals one board foot. For a batch of identical boards, calculate one board first, then multiply by the number of pieces. Extension guidance on timber measurement, such as Virginia Tech Extension's forest landowner guide to measuring timber and logs, uses the same volume basis and shows how board-foot rules also apply when logs — not just finished boards — are being scaled and sold.
Three habits keep the formula accurate:
- Use consistent units. Mixing a length in inches into the divide-by-12 version is the most common error, and it inflates the answer twelvefold.
- Measure the board you are paying for. For rough lumber, use the actual rough dimensions. For surfaced lumber, yards generally tally by the nominal size the board was before surfacing — ask the seller which convention applies before you argue over a tally.
- Round the way the trade does. Individual boards often come out to fractions; a total order is normally rounded to the nearest whole board foot for invoicing.
Worked Examples: How to Calculate Board Feet Step by Step
Example 1 — a single board. A rough oak board measures 1 inch thick, 8 inches wide and 10 feet long. Multiply 1 × 8 × 10 = 80, then divide by 12: 6.67 board feet.
Example 2 — a framing stud. A nominal 2×4, 8 feet long: 2 × 4 × 8 ÷ 12 = 5.33 board feet. Note that a surfaced 2×4 actually measures about 1.5 × 3.5 inches — which is why the nominal-versus-actual question matters, and why buyers and sellers should agree the tally basis up front.
Example 3 — thick stock. A 2-inch-thick (8/4) walnut board, 10 inches wide and 6 feet long: 2 × 10 × 6 ÷ 12 = 10 board feet. Thick, wide hardwood stock adds up fast, which is why a handful of slabs can carry a surprising price tag.
Example 4 — a whole order. You need forty boards, each 1 × 6 × 12 feet. One board is 1 × 6 × 12 ÷ 12 = 6 board feet, so the order is 40 × 6 = 240 board feet. At an illustrative price of $4.50 per board foot, that order costs 240 × $4.50 = $1,080 before tax or delivery — an example figure to show the method, not a market quote.
Board Foot Chart for Common Sizes
For standard sizes, the chart below does the arithmetic for you. Figures are board feet per board, using nominal dimensions.
| Nominal size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1 × 4 | 2.67 | 3.33 | 4.00 | 5.33 |
| 1 × 6 | 4.00 | 5.00 | 6.00 | 8.00 |
| 1 × 8 | 5.33 | 6.67 | 8.00 | 10.67 |
| 1 × 12 | 8.00 | 10.00 | 12.00 | 16.00 |
| 2 × 4 | 5.33 | 6.67 | 8.00 | 10.67 |
| 2 × 6 | 8.00 | 10.00 | 12.00 | 16.00 |
| 2 × 8 | 10.67 | 13.33 | 16.00 | 21.33 |
| 2 × 10 | 13.33 | 16.67 | 20.00 | 26.67 |
| 2 × 12 | 16.00 | 20.00 | 24.00 | 32.00 |
| 4 × 4 | 10.67 | 13.33 | 16.00 | 21.33 |
A useful shortcut hides in the chart: a 1 × 12 or a 2 × 6 contains exactly one board foot per linear foot, so for those sizes the board footage simply equals the length in feet. A 1 × 6 holds half a board foot per foot, and a 2 × 12 holds two.
Hardwood Thickness Is Quoted in Quarters
Hardwood lumber is usually sold by quarter measure rather than plain inches: 4/4 means 1 inch thick, 5/4 means 1.25 inches, 6/4 means 1.5 inches, 8/4 means 2 inches, and 12/4 means 3 inches. Use the full quarter figure — the “1” in 4/4, the “2” in 8/4 — as the thickness in the formula, because rough hardwood is tallied on its pre-surfacing thickness. A 5/4 board 7 inches wide and 9 feet long, for example, is 1.25 × 7 × 9 ÷ 12 = 6.56 board feet.
How to Calculate Board Feet in a Log
Boards are easy; logs take one extra idea. A log's board-foot content is an estimateof the lumber it should yield, worked out from the small-end diameter inside the bark and the log's length, using a log rule. The three rules in common North American use are Doyle, Scribner and International 1/4-inch, and they do not agree — especially on small logs, where the Doyle rule runs notably low. Penn State's forestry mensuration material sets out the standard log-scale tables, and Virginia Tech's guide makes the commercial point plainly: the same 16-inch, 16-foot log scales at 180 board feet on the International rule, 160 on Scribner Decimal C and 144 on Doyle — a spread that changes what the log is worth at any given price per thousand board feet.
Two practical consequences follow. First, whenever you buy or sell logs, state the rule in the agreement, not just the price. Second, remember that log scale is an estimate of yield, not a promise: a band mill with a thin kerf, careful sawing and sound logs can recover more lumber than the scale suggests, while defects, sweep and rot pull recovery down. Sawyers buying logs for their own mill should still tally the boards that actually come off the mill and price their finished lumber from that tally.
From Board Feet to a Price
Once you can calculate board feet, pricing becomes a single multiplication: total board feet × price per board foot = lumber cost. The skill is in making sure both sides of a deal are counting the same thing.
- Buying lumber: ask for the tally by board foot, the tally basis (rough or nominal), and the price per board foot. Recalculate a sample of boards before you pay — honest sellers welcome it.
- Selling lumber: publish your price per board foot by species and grade, and show your tally on the invoice. Sellers listing equipment or lumber through Lumber Lookup's selling pages can also check the site's pricing guidance to see how listing options are structured.
- Hiring custom sawing: many sawyers charge by the board foot sawn, so your tally is the invoice. Agree in advance whether the charge is based on the lumber tally or the log scale — the two numbers are rarely the same.
- Adding waste: for project buying, add an allowance for defects, edging and planing loss. Lower grades carry more unusable area, so they need a larger allowance than clear, high-grade stock bought for the same finished job.
If you are costing out the mill that produces those boards, our breakdown of portable sawmill prices shows what the equipment side of the equation looks like, and our guide on how to start a sawmill business works through turning board-foot output into a business.
Common Mistakes When You Calculate Board Feet
- Using the length in inches with the ÷12 formula. That overstates volume twelve times over. Either convert length to feet or divide by 144.
- Measuring surfaced lumber at its finished size when the yard tallies nominal. A planed 2×4 is not 2 × 4 inches any more. Neither side is cheating — but you must count the same way the invoice does.
- Forgetting the piece count. The formula prices one board. Multiply by the number of identical pieces, and calculate mixed sizes line by line.
- Treating log scale as exact. Log rules are conventions for estimating yield. State the rule, and expect real recovery to vary with log quality and sawing.
- Ignoring kerf and surfacing loss in your own milling estimates. A log that scales at 200 board feet will not give you 200 board feet of finished, planed lumber.
Conclusion: How to Calculate Board Feet with Confidence
Learning how to calculate board feet takes one formula — thickness × width × length in feet, divided by 12 — plus the discipline to agree on the tally basis before money changes hands. Run the numbers on every quote, check a sample of boards against every invoice, and keep the chart above near the mill or the desk. When you are ready to put those calculations to work, browse the forestry and lumber equipment marketplace at LumberLookup.com — mills, edgers and handling gear are listed by category, so you can match the machine to the board footage you actually need to produce.