Calculate Board Feet to Linear Feet
Convert board feet into linear feet accurately by entering the lumber thickness and width. This premium calculator is ideal for estimating stock requirements for trim, casing, shelving, hardwood, softwood, and custom millwork.
Linear Feet = (Board Feet × 12) ÷ (Thickness in inches × Width in inches)
Example: 100 board feet.
Enter actual or nominal thickness based on your estimating method.
Width of the board face.
If you choose millimeters, the calculator converts to inches automatically.
Estimated output
Linear Feet Conversion Chart
The chart below compares how many linear feet you get at multiple board-foot levels using your selected width and thickness. This helps visualize inventory planning for larger runs.
Expert Guide: How to Calculate Board Feet to Linear Foot Accurately
Understanding how to calculate board feet to linear foot is essential for anyone who buys, sells, mills, installs, or budgets lumber. Carpenters use the conversion to estimate trim runs, furniture parts, and framing stock. Woodworkers rely on it when pricing rough hardwood. Builders need it to compare material quotes across suppliers. Even homeowners benefit because lumber can be sold in one measurement while a project plan is drawn in another. If you know how to move between board feet and linear feet correctly, you can estimate material use faster, reduce waste, and avoid under-ordering or overpaying.
The most important thing to understand is that board feet and linear feet are not interchangeable by themselves. A board foot measures volume, while a linear foot measures length. Because board feet include thickness, width, and length, you cannot convert board feet to linear feet unless you also know the board’s thickness and width. That is why every accurate conversion tool asks for those dimensions first. Once thickness and width are known, the conversion becomes straightforward and very reliable for practical estimating.
What is a board foot?
A board foot is a standard unit of lumber volume equal to a board that is 1 inch thick, 12 inches wide, and 1 foot long. In formula terms:
- 1 board foot = 144 cubic inches
- Board feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12
This unit is common in hardwood yards, sawmills, and specialty lumber sales because it accounts for the full amount of wood in a board rather than just its visible length. It is especially useful when boards come in mixed widths and lengths.
What is a linear foot?
A linear foot is simply a measure of length equal to 12 inches. It does not include width or thickness. If you buy 20 linear feet of molding, you are buying 20 feet of length. The profile may be narrow or wide, but the linear-foot number itself only represents distance. This is why linear footage is common for trim, baseboards, handrails, decking, and fencing, where installation planning is usually based on run length.
The exact formula for converting board feet to linear feet
The core equation is:
Linear Feet = (Board Feet × 12) ÷ (Thickness in inches × Width in inches)
This works because the board-foot formula includes length. When you rearrange the standard lumber formula to solve for length, you get linear feet. For example, suppose you have 100 board feet of lumber that is 1 inch thick and 6 inches wide:
- Multiply board feet by 12: 100 × 12 = 1,200
- Multiply thickness by width: 1 × 6 = 6
- Divide: 1,200 ÷ 6 = 200
So, 100 board feet of 1 inch by 6 inch stock equals 200 linear feet.
Step-by-step method used by professionals
- Measure thickness carefully. Decide whether you are using nominal or actual dimensions. For rough lumber, nominal dimensions are often used in yard calculations. For surfaced lumber, actual thickness may matter more.
- Measure width consistently. Use the same dimension basis throughout your estimate. Mixing actual and nominal widths can create costly errors.
- Confirm your board-foot quantity. This may come from a supplier invoice, a mill tally, or your own volume estimate.
- Apply the conversion formula. Multiply board feet by 12, then divide by thickness times width.
- Add a waste factor. In real jobs, defects, end trimming, knots, grade issues, and pattern matching increase usable-loss percentages.
Common examples for fast field estimating
Below are sample conversions using the same 100 board feet across different board sizes. These examples show why width and thickness matter so much.
| Board feet | Thickness | Width | Formula | Linear feet |
|---|---|---|---|---|
| 100 | 1 in | 4 in | (100 × 12) ÷ (1 × 4) | 300 ft |
| 100 | 1 in | 6 in | (100 × 12) ÷ (1 × 6) | 200 ft |
| 100 | 1 in | 8 in | (100 × 12) ÷ (1 × 8) | 150 ft |
| 100 | 2 in | 6 in | (100 × 12) ÷ (2 × 6) | 100 ft |
| 100 | 2 in | 10 in | (100 × 12) ÷ (2 × 10) | 60 ft |
Notice the pattern: as thickness or width increases, the resulting linear footage goes down for the same board-foot amount. That makes sense because a larger cross-section consumes more wood per foot of length.
Nominal vs actual dimensions matter more than many buyers realize
One of the biggest mistakes in board-foot conversion is confusing nominal dimensions with actual dimensions. In many retail settings, a board called “1×6” does not actually measure 1 inch by 6 inches after surfacing. Actual dimensions are often smaller. For hardwood sold rough, dimensions may be closer to nominal before milling. For planed softwood boards, actual dimensions are typically reduced. This difference directly changes your linear-foot result.
For example, using 100 board feet:
- If you estimate a “1×6” as 1 inch × 6 inches, you get 200 linear feet.
- If the actual dressed dimensions are about 0.75 inch × 5.5 inches, the estimate becomes about 290.9 linear feet.
That is a large difference. It shows why professional estimators decide on a dimension standard before ordering material. If the yard sells by rough volume but the job installs surfaced stock, build your estimate around the stage of production that matters for your purchase and yield expectations.
Practical waste factors for real jobs
In jobsite conditions, exact mathematical output is only part of the picture. Cutting loss, damaged ends, grain selection, color matching, knots, and defects all reduce usable footage. In trim work, a simple room layout may only need a 5% waste factor. In custom cabinetry, high-grade hardwood, or projects with many miters and short cutoffs, 10% to 20% is more realistic. Using a built-in waste factor helps bridge the gap between textbook volume and real usable material.
| Project type | Typical waste allowance | Why it varies | Best use case |
|---|---|---|---|
| Straight trim runs | 5% | Fewer complex cuts and low defect exposure | Baseboard, simple casing, wall runs |
| General finish carpentry | 10% | Standard fitting, coping, and selection loss | Average residential interior projects |
| High-end millwork | 15% | Color match, grain continuity, premium appearance requirements | Custom built-ins and hardwood detailing |
| Irregular stock or difficult layouts | 20% | More defects, short cutoffs, complicated geometry | Reclaimed lumber and specialty installations |
Why board feet is still a standard in the lumber trade
Board-foot pricing remains common because it allows yards and mills to standardize transactions across boards of different lengths and widths. Instead of pricing each board shape separately, a seller can assign value per unit of wood volume. This is especially helpful when dealing with hardwoods, live-edge slabs, and rough-sawn material. Buyers can then convert the purchased volume into expected linear footage for specific dimensions used in their projects.
Forest product research institutions and extension services regularly discuss lumber sizing, grading, and measurement methods because accurate sizing improves value recovery and purchasing decisions. For additional reference, you can review resources from the U.S. Forest Service, the USDA Forest Products Laboratory, and extension guidance from Penn State Extension.
Metric conversions: using millimeters for thickness and width
Some shops and international suppliers work in millimeters rather than inches. That is not a problem as long as the dimensions are converted correctly before using the board-foot formula. Since board feet are defined in inch-based volume terms, thickness and width measured in millimeters should be converted to inches first by dividing by 25.4. The calculator above handles that automatically when you select millimeters. This is convenient for cabinetmakers, CNC shops, and imported stock comparisons.
Frequent mistakes that lead to bad estimates
- Ignoring thickness. You cannot estimate linear feet from board feet using width alone.
- Mixing actual and nominal dimensions. This is one of the most common causes of overbuying or underbuying.
- Forgetting waste. Clean formulas do not account for trim-offs, defects, or layout inefficiencies.
- Rounding too early. Keep decimal precision until the final number, especially on expensive hardwood jobs.
- Assuming all boards yield equally. Grade, moisture, warp, and defects affect practical usable footage.
When to use board feet vs linear feet
Use board feet when purchasing rough or mixed-dimension lumber, pricing hardwood, or evaluating stock volume. Use linear feet when laying out runs, estimating installed trim lengths, or comparing footage requirements from plans. On many projects you will use both: board feet to buy, linear feet to install. The conversion connects the supply side to the construction side.
Simple rule of thumb for quick checks
If thickness and width stay constant, linear footage increases in direct proportion to board feet. Double the board feet and you double the linear feet. Also, if the board cross-section doubles, the linear footage is cut in half for the same board-foot quantity. This quick mental framework is useful when checking supplier quotes or validating a crew estimate in the field.
Final takeaway
To calculate board feet to linear foot correctly, always begin with the board-foot quantity, then divide by the board’s cross-sectional size using the standard formula. Consistent dimensions, realistic waste factors, and clear understanding of nominal versus actual sizes are what separate dependable estimates from expensive mistakes. Whether you are ordering walnut for custom shelving, pine for trim, or oak for stair parts, the right conversion helps you budget better, compare quotes intelligently, and keep your project moving without unnecessary material overruns.
If you need a fast result, use the calculator above. Enter board feet, thickness, width, and your preferred waste allowance. You will get an immediate estimate of linear footage plus a chart to visualize how your selected board size scales across larger or smaller stock quantities.