A single board foot of lumber measures 1 inch thick, 12 inches wide and 12 inches long. The formula for calculating board feet is first to multiply thickness by width by length — in inches. Then divide the total by 144 for the total board footage of a given board.
Board Foot Formula is the Most Important Lumber Calculation
Estimating board footage (or board feet) is the most important math hardwood lumber buyers and sellers perform. Thus, a board foot calculator is critical. Accurately counting and estimating hardwood lumber is a critical calculation. Thus, knowing the board foot formula is extremely important.
When figuring board feet incorrectly, bad things happen:
Over the course of my hardwood lumber career all of these things have happened to me. Lumber count discrepancies are always embarrassing and sometimes costly, especially in figured woods and exotics. However, wood count discrepancy claims are almost always preventable.
Hardwood Lumber Board Foot Calculator
Enter the length, width, and thickness of the hardwood board (inches):
Result:
What is a Board Foot?
The board foot or board-foot is a unit of measurement for the volume of lumber in the United States and Canada. It equals the volume of a one-foot (305 mm) length of a board, one foot wide and one inch (25.4 mm) thick. Board foot can be abbreviated as FBM (for “foot, board measure”), BDFT, or BF
Not a lot of math is needed to estimate hardwood lumber. However, there are a few important concepts to understand.
Typically, people are used to counting things in a lineal way or by the piece.. Lineal calculations involve distance or length only. Pieces are typically uniform-sized objects, like pool cue blanks, for example..
Lineal counts work well when you are estimating a fixed width and fixed thickness product.
Square footage is an area calculation. It accounts for variations in both length and width but not thickness. Thus, it works well for flooring calculations
Board footage is a volume calculation. Measuring in board feet accounts for varying thicknesses, widths and lengths. Wood density is not a factor in figuring board feet. Thus, light weight hardwoods like Balsa wood and dense/heavy hardwoods such as iroko or ebony measure BF the same way.
Hardwood lumber boards like poplar or purpleheart, for example, are usually packaged in mixed width and mixed length bundles.
The irregular dimensions of hardwood lumber boards result in gaps and voids in the units that must be accounted for. In contrast, 1 x 6 x 8 Pine S4S boards fit together flush and seamlessly in uniform bundles.
What do we mean by tally length? In lumber terms, it is the length of the board for the purposes of measuring, not necessarily the actual board length.
For example, hardwood lumber board lengths are often rounded up or down for tallying purposes. Boards cut at 98″ may be tallied as 8′ rather than 8 feet and two inches.
Price per Board Foot Lumber
Hardwood lumber is typically priced by the board foot, rather than by the piece or lineal foot.
The reason for this is that hardwood lumber is usually sawn into random width boards. Whereas, softwoods like pine, spruce and Douglas Fir are often sawn and packaged in a single dimension 2x4x8′, for example.
Accordingly, knowing the board foot price allows hardwood buyers & woodworkers to calculate the value of lumber units assuming they also can tally the board footage!
Hardwood Lumber Tally Secrets
Here are a few trade secrets of lumber tallying that I will share with you:
The hardwood lumber tally stick of one of my lumber mentors, Stan Buck (Crossland Forest Products). Courtesy of Ann Barwick Jones.
Using a tally stick to count hardwood lumber is the best way to estimate lumber in board feet. However, many lumber professionals lack the knowledge or desire to use one.
Some shady lumber companies take advantage of customers by intentionally spacing out boards within the unit. Customers often fail to account for extra wide gaps when doing a quick block tally. Essentially, customers pay for air as if it is wood.
Whilehardwood grades are uniform, there is variation among sawmills in their lumber tally methodology. Some sawmills tally 7 1/2″ wide boards on an 8″ count. Other mills count an 8’5″ long board as 8′. Don’t assume anything. Verify and keep notes on how each supplier tallies. Otherwise, you will be unable to accurate compare their offerings.
All sawmills use the same thickness rules (4/4, 5/4, 6/4, 8/4, etc). However, not all sawmills cut rough lumber at the same thickness. For example, 5/4 rough-sawn lumber may be 1 1/4-1 3/8″ from one supplier and 1 1/4″ +-1/16″ from another. As a general rule, modern sawmills cut to tighter tolerances than older ones. Therefore, mills using older equipment cut their boards thicker to account for less precise machining. According to the National Hardwood Lumber Association, 5/4 lumber needs to clean up at 1″ net after machining otherwise it is considered scant. Basically, to maximize their yield, sawmills will produce as close to scant as their machinery will allow. Accordingly, plump cut lumber from old circle mill operations give you extra thickness at no charge. Sawmills don’t make it like they used to…if they can help it!
Calculate Board Feet with Board Feet Formula
First, measure the length of the board in feet.Use the exact measurements, in feet. For example, if you measure 12′ 3″ long, record the length as 12.25′
Next, measure the width of the board in inches. Again, measure as accurately as possible. If the board tapers in width from one end to the other, measure the width at both ends and divide by 2 to calculate the average width.
Then, measure the count (board thickness) in quarters of an inch. However, for this calculation, round up to the nearest quarter, assuming the lumber is surfaced. If the lumber is rough, record it at the closest 1/4″. Thus, if your tape measure reads 1.875″ on surfaced lumber, the count is 8/4 (leave as a fraction, do not reduce it to 2) Most board footage calculation errors result from a discrepancy related to the count. Unlike the width and length, the count is not an exact measurement. The exact measurement is rounded into quarters. Additionally, there are some anomalies that are not intuitive. For example, if the thickness of a board measures 1.625″, it rounds all the way up to 8/4 count unless the seller states it is being sold on a 7/4 count. Typically, hardwood lumber is measured on the following counts: 4/4, 5/4,6/4,8/4, 10/4,12/4,16/4. Occasionally, lumber is sold on an atypical count such as 3/4,7/4,9/4, 14/4, etc. However, this is the exception rather than the rule. If there is any question ask the seller “What count are you using to tally?” A 10% price discount on hardwood lumber that has been tallied on a lower thickness count is a price hike!
Next, multiply width (inches) x length (feet) x count
Finally, divide the result by 12
This is a step-by-step guide to your board feet formula.
127 Board Feet 6/4 Ambrosia Figured Maple being tallied.
Block Tallying Lumber: Fast Way to Estimate Bundle Size
Calculating board footage like we did above is accurate but slow. Block tallying or bundle tallying lumber is a fast way to estimate total board feet when you have a unit or bundle of lumber rather than a few boards.
Lumber Inventory Accounting
If you are doing a yard inventory count you may need to check 50-75,000 board feet in a day. The objective of inventory is to find missing units or significantly incorrect board footage quantities. A block tally is the best way to do this.
How to Block Tally Lumber
Measure the width of the lumber unit in inches. If the bundle is stacked poorly, measure an area that looks about average, not the widest or narrowest course.
Reduce the width by the approximate distance of gaps between boards. In a well stacked random width hardwood lumber unit, this is usually 2-4″.
Measure the average length of the unit in feet. If a unit if hardwood lumber is mixed length, there should be one flush end and one end with varying lengths. After measuring the longest board, visually estimate how many trim-backs from the uneven end of the unit. Often, individual hardwood lumber bundles are sorted into these length ranges 6-8′, 9-10, 11-12′, 13-16′. Additionally, lengths often run 80-90% to the longest length of the bundle. Thus, a common length average for a 9-10′ bundle may be 9.8′.
Measure the thickness to determine the board count (thickness in quarters, as described above). Typically hardwood lumber is bundled in uniform count thicknesses.
Count the number of courses or layers of boards in the unit.
Multiply the average course width (inches) x average course length (feet) x thickness count
Divide the result by 12.
Multiply the result by the number of courses.
Practice block tallying by trying it on lumber bundles that have already been accurately tallied. Then compare your estimate to the actual board feet. With a little practice, your block tallies will be consistently close to actual tallies.
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Board Foot Calculator
The board feet calculator below quickly allows you to estimate hardwood lumber volumes. Omni’s BF calculator easily calculates hardwood lumber requirements.
Simply enter your lumber thickness, width, length, and quantity and it will calculate the board footage.
Board Foot Calculator
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