Board Foot Calculator
Fill in all required fields then click the Calculate button to see your board foot results instantly. The total will keep updating until you reset the calculator.
| # | Pieces | Thick (in) | Width (in) | Length (ft) | BF/Piece | Total BF | Cost |
|---|
Board Foot Calculator: Calculate Lumber Volume and Cost
Find out just how much lumber you need and what the cost will be with our free board foot calculator. This page will walk you through the math in plain language whether you are buying lumber for a furniture project or trying to estimate how much usable lumber you can get from a log or standing tree. You will learn how to calculate board feet, how it differs from a linear foot or square foot, how to do the math by hand, and how to convert it all to metric if you are shopping outside the US or Canada. We’ve also included a separate section on log and tree board-foot estimating because that’s a very different calculation than milled lumber.
What Is a Board Foot?
A board foot measures volume, not length or area. A board foot is a piece of lumber 12 inches long, 12 inches wide and 1 inch thick. That is 144 cubic inches of wood. The actual shape of the board is not important. If it is 144 cubic inches, it is one board foot. If the total volume of a long, thin board and a short, thick board is the same, they can be exactly one board foot calculator.
This measurement is important because it is the standard unit used to price hardwood lumber throughout the United States and Canada. Instead of pricing by the piece or by length alone, sellers price wood by volume, which takes into account both size and thickness at the same time. That’s why you should know about board feet, not just linear feet, before you buy.
Board Feet vs. Linear Feet vs. Square Feet
These three terms are confused all the time, but they measure very different things. A linear feet calculator that’s all about distance. Whether it is an inch thick or a foot thick, a 10-foot board is 10 linear feet. Area is length multiplied by height, and a square foot is a unit of area. A board foot calculator takes this one step further and adds in the thickness, giving you the actual amount of wood.
Measurement | What It Measures | Typical Use |
Linear foot | Length only (1 dimension) | Trim, molding, softwood dimensional lumber sold by length |
Square foot | Area (2 dimensions: length × width) | Flooring, decking, sheet goods |
Board foot | Volume (3 dimensions: length × width × thickness) | Hardwood lumber, rough-cut boards, slabs (pricing accounts for thickness) |
Say you have a board that is 9 feet long, 7 inches wide and 1.25 inches thick.
- It’s only 9 linear feet. A linear foot is a measurement.
- It covers about 5.25 square feet as a square foot measurement (not counting thickness) (7 inches ÷ 12 × 9 feet).
- As a board foot measurement (including thickness) it is about 6.56 board feet.
Same board, three very different figures. That’s exactly why a linear feet calculator and a board foot calculation will never give you the same answer for the same piece of wood.
How to Calculate Board Feet: The Formula
Once you have the formula, calculating board feet is a snap. If your height is measured in feet:
Board Feet = (Thickness in inches x Width in inches x Length in feet) / 12
Use this version if you are measuring length in inches rather than feet:
Board Feet = (Thickness x Width x Length in inches) / 144
Both formulas will yield the same result. They are just based on different units of length.
Worked example Say you are buying a piece of walnut 5/4 (1.25 inches) thick, 7 inches wide and 9 feet long.
Board Feet = (1.25 x 7 x 9) / 12 Board Feet = 78.75 / 12 Board Feet = 6.56 board feet
That one number tells you exactly how much wood you are buying no matter how weird the thickness or width of the board. That’s why the formula is so useful; it allows you to fairly compare prices across boards of wildly different shapes and sizes, which is why board feet exist as a pricing unit in the first place.
If you ever need to figure board feet fast without doing the math by hand our calculator above does this instantly. You enter the thickness, width and length and it gives the total.
Board Foot Calculator: Multiple Pieces and Total Cost
Most real projects require more than one board, so the next step is to scale the formula up. Once you know the board footage of one piece, multiply it by the number of identical pieces you are buying. Then multiply that total by your supplier’s price board per foot calculator to arrive at your full project cost.
Total Board Feet = Board Feet per Piece * Number of Pieces Total Cost = Total Board Feet * Price per Board Foot
Example: Suppose you want 12 pieces of oak, 2 inches thick, 5 inches wide, and 6 feet long, and your supplier charges $7.50 per board foot.
Board Feet per piece = (2 × 5 × 6) / 12 = 60 / 12 = 5 board feet Total Board Feet = 5 x 12 = 60 board feet Total Cost = 60 x $7.50 = $450
Hardwood prices vary a great deal by species, region and supplier, so consider any per-board-foot price you see online as a general starting point, not a fixed number. Always check with your local timber yard for current prices before ordering.
Nominal vs. Actual Dimensions: A Common Accuracy Mistake
One of the easiest mistakes to make can throw off your entire calculation. Dimensional softwood lumber (the kind used for framing, like a standard “2×4”) is sold by a nominal size that is larger than what you actually receive. A 2×4 that has been milled and dried is not really 2 inches by 4 inches anymore. It is more like 1.5 inches by 3.5 inches.
Using the nominal size instead of the actual size in the board foot calculation will give a much too high result. Always use the actual, measured dimensions of dimensional lumber (i.e., 1.5″ × 3.5” for a “2 × 4”), not the name printed on the label.
Hardwood is different. First of all, it is usually sold and measured in actual rough-cut dimensions, so what you measure is generally what you calculate with, and no adjustment is necessary. Rule of thumb: one of the most common reasons a board-foot total comes up wrong is if you’re buying dimensional softwood (adjust to actual size) or hardwood (use the measured size straight up).
Rounding and Waste: Ordering the Right Amount
Add a couple of small conventions to make your final number a bit more realistic. For dimensional softwood lumber, always round up to the next whole foot for each board’s length before you calculate. Lumber is usually cut in full-foot increments, so an 8-foot-4-inch board should be counted as 9 feet.
Do not round for hardwood It is usually sold by exact board footage, so use exact inches for thickness, width and length, not rounding up or down.
Finally, no matter what you’re building, it’s a good idea to add around 10-15% more to your total board footage. This includes offcuts, measuring errors and any boards with defects you’ll have to cut out around. For the above oak project (60 board feet), a 12% waste factor would push your order to about 67.2 board feet. Better to have a little extra than to run out mid-project.
Board Feet in Metric: A Note for UK, Australian & Canadian Readers
Board feet is a North American convention. If you are shopping for timber in the UK or Australia, you will rarely see wood priced this way. The standard is cubic meters instead. Here is your translation:
1 board foot ≈ 0.00236 m³ (2,360 cm³)
If you prefer to just skip the inches conversion and stick with metric, try this formula instead, where all dimensions are in centimeters:
Volume in cubic meters = (Thickness in cm x Width in cm x Length in cm) / 1,000,000
Worked example: A board that is 3 cm thick, 18 cm wide and 240 cm long:
Volume=(3 x 18 x 240)/1,000,000=12,960/1,000,000=0.01296 cubic meters
To convert that back to board feet to compare to a US or Canadian supplier’s pricing, divide by 0.00236: 0.01296 ÷ 0.00236 = ~5.49 board feet. That allows shoppers in Canada, the UK and Australia to compare quotes from either side of the Atlantic without doing a separate sum each time.
Log Board Foot Calculator: Estimating Yield From a Log or Standing Tree
This is where it all changes entirely. The milled-lumber formula above works for boards that have already been cut but does not apply to a whole log or a standing tree. A round log loses a lot of its volume to bark, taper (the log gets smaller as you go up), the rounded outer edges (called slabs), and the saw blade itself, which takes a very thin strip of wood (called kerf) with every cut.
Instead, foresters and log buyers estimate the actual yield of usable timber from a log by using log scaling rules. The Doyle rule, the Scribner rule, and the International 1/4-inch rule are the three most common. The Doyle rule, which dates back to the early 19th century and is attributed to Edward Doyle, is still common in the eastern and southern United States today, though it is known to underestimate yield on smaller logs. The Scribner and International 1/4″ rules are two long-standing U.S. forestry log scaling methods designed to better approximate actual sawmill output.
Log Rule | Formula (D = small-end diameter inside bark, in.; L = length, ft) | Typical Tendency |
Doyle Rule | Board Feet = (D − 4)² × L ÷ 16 | Tends to underestimate yield on smaller-diameter logs; still common in the eastern/southern US |
Scribner Rule | Board Feet ≈ (0.79 × D² − 2D − 4) × L ÷ 16 | Often tracks closer to actual mill yield than Doyle on mid-size logs |
International 1/4″ Rule | Tabulated/taper-adjusted formula accounting for 1/4-inch saw kerf | Generally considered the most consistent versus modern mill yield |
Think about a log that is 12 feet long and 14 inches across at the widest point.
Doyle (14.4) x 12 x 16 = 100 x 12 x 16 = 75 board feet Scribner: (0.79 × 14² − 2 × 14 − 4) × 12 ÷ 16 = (154.84 − 28 − 4) × 12 ÷ 16 = 122.84 × 12 ÷ 16 ≈ 92.
The two rules on the same log are different by about 23%. That’s why the rule you (or your buyer) follow is so important. There is no exact, surefire way to follow any of these rules. The milled yield in real life still depends on the taper of the log, any flaws inside, and how much wood is cut off by the saw’s kerf. It’s never a promise when you use the log rule to figure something out.
Frequently Asked Questions
Q1. What’s the difference between a board foot and a linear foot calculator?
A linear foot is a measure of length only. It doesn’t care how thick or how wide the board is. A board foot is a unit of volume that includes length, width and thickness. So two boards that are the same length can have very different board footage once you know how wide or how thick they are.
Q2. How to calculate board feet for a log or standing tree instead of a milled board?
Instead of the standard milled timber formula, whole logs and standing trees are measured using a log scaling rule (Doyle, Scribner, International 1/4″, etc.). These rules take into consideration taper, saw kerf, and slab waste, which cannot be accounted for by a simple length-width-thickness calculation. Different rules can give very different estimates for the same log, so it’s useful to know which one your buyer or mill is using.
Q3. Should I use nominal or actual dimensions to calculate board feet?
For dimensional softwood lumber, like a construction grade ’24’, the nominal name is always bigger than the real dimensions. So use the actual planned size (about 1.5″ x 3.5”) for an accurate result. Hardwood is generally sold and measured in its actual rough-cut size already, so you can use the measured dimensions as is.
Q4. How much extra lumber should I buy beyond my calculated board footage?
A common rule of thumb is to add 10-15% to your calculated total. It allows for defects, offcuts and small measuring errors and is especially useful on projects with lots of cuts or tight joinery, where mistakes are more likely to eat into your material.
Q5. Why do the Doyle and Scribner log rules give different board foot estimates for the same log?
Each rule has different assumptions on slab waste, taper and saw kerf. The Doyle rule tends to underestimate yield on small diameter logs, whereas the Scribner rule tends to come closer to real sawmill output on mid-size logs. Or put another way, the same log can be legitimately scored in different ways, depending on which rule you choose. They’re just making different assumptions and aren’t “wrong” as such.
Q6. How do I convert board feet into a total lumber cost?
You take the board footage of one piece and multiply it by the number of pieces you need and that is your total board footage. Multiply that number by the price your supplier charges per board foot. Add a waste allowance to the total board footage before this last multiplication to get a more realistic cost of the project.
Conclusion
Board foot calculator doesn’t have to be confusing. Once you know it’s a volume measurement (not length or area) the formula is simple to apply whether you are pricing a stack of hardwood boards, estimating the yield of a log or converting everything into metric units for a UK or Australian project. Here you get all three plus the little details (nominal vs. actual sizes, rounding, waste) that most calculators miss. Want to see your numbers? Use the board foot calculator above to instantly get a total for your project.