If you have ever walked into a lumber yard and heard one supplier quote “$3 per linear foot” and another quote “$8 per board foot” for what looked like similar wood, you have run into one of the most common sources of confusion in lumber estimating. The two units measure different things, and using the wrong one will either leave you short of material or overspending by hundreds of dollars on a project.
Linear feet (LF) measures length. Board feet (BF) measures volume. Both are valid, both are used every day in the construction trades, but they apply to different categories of lumber and serve different estimating purposes. This guide breaks down when to use each, how to convert between them, and the practical mistakes that cost contractors and DIYers real money.
Quick answer
| Linear feet | Board feet |
|---|---|
| Measures length only | Measures volume (thickness × width × length) |
| Used for trim, molding, fencing, dimensional softwoods | Used for hardwood lumber, rough-sawn timbers, slabs |
| A 10-foot 2×4 = 10 linear feet | A 10-foot 2×4 = 6.67 board feet |
| Sold by the foot, priced per linear foot | Sold by BF, priced per BF |
| Ignores thickness and width | Accounts for all three dimensions |
What is a linear foot?
A linear foot, also called a running foot, is simply 12 inches of length. It ignores thickness and width entirely. If you measure a piece of trim, molding, baseboard, or fence rail in linear feet, you are measuring how long it is, nothing more.
Linear feet shows up most often in:
- Trim and molding: crown, baseboard, casing, chair rail, shoe molding
- Dimensional lumber sold by the piece: 2x4s, 2x6s, 2x8s in standard lengths
- Fencing materials: rails, posts, pickets
- Roofing components: fascia, drip edge, soffit material
- Cabinetry hardware: drawer slides, hinges (some manufacturers)
The advantage of linear feet is simplicity. You do not need to know thickness, width, or grade to calculate how much you need. If a wall is 24 feet long and needs baseboard, you need 24 linear feet of baseboard plus a small waste allowance. Done.
What is a board foot?
A board foot is a volume measurement equal to 144 cubic inches: one inch thick, twelve inches wide, twelve inches long. Unlike linear feet, BF accounts for the full three dimensions of a piece of lumber. A board that is two inches thick contains twice the wood by volume as a one-inch board of the same width and length, so it costs twice as much per BF, all else equal.
Board feet shows up most often in:
- Hardwood lumber: oak, walnut, cherry, maple, mahogany sold for furniture, cabinetry, and millwork
- Rough-sawn softwoods: timbers, beams, and specialty cuts sold by the BF rather than by piece
- Live edge slabs: priced per BF based on average thickness
- Mill direct sales: most sawmills sell all lumber by BF regardless of species
- Cabinet shop estimating: where complex projects need accurate material costing
- Custom millwork: where each piece has unique dimensions
The advantage of board feet is accuracy across mixed sizes. If you are building furniture from boards of varying widths (which is normal for hardwoods), BF gives you a single unit to compare prices, calculate totals, and verify supplier invoices.
For exact BF calculations on any lumber, the free board foot calculator handles thickness, width, length, quantity, waste, and cost in one tool.
How to convert between linear feet and board feet
The conversion depends on the cross-sectional area of the lumber (thickness times width). Use this formula:
Board feet = (Linear feet × Thickness in inches × Width in inches) / 12
A few worked examples:
Example 1: A 10-foot 2×4 (softwood dimensional)
Nominal dimensions: 2 inches by 4 inches by 10 feet
BF = (10 × 2 × 4) / 12 = 80 / 12 = 6.67 BF
So a 10-foot 2×4 is 10 linear feet and 6.67 board feet. Same piece of wood, two different measurements.
Example 2: An 8-foot piece of 4/4 hardwood, 6 inches wide
Nominal dimensions: 1 inch by 6 inches by 8 feet
BF = (8 × 1 × 6) / 12 = 48 / 12 = 4 BF
This is also 8 linear feet, but only 4 board feet.
Example 3: A 12-foot 2×6
Nominal dimensions: 2 inches by 6 inches by 12 feet
BF = (12 × 2 × 6) / 12 = 144 / 12 = 12 BF
12 linear feet, 12 board feet. They happen to match here because the cross-section equals 12 square inches.
The reverse conversion (BF to linear feet) requires you to know the thickness and width:
Linear feet = (Board feet × 12) / (Thickness × Width)
When to use linear feet vs board feet
Use the table below to decide which unit applies to your project:
| Situation | Use this unit | Why |
|---|---|---|
| Buying trim, molding, or baseboard | Linear feet | Cross-section is fixed by the profile, you only need length |
| Buying 2x4s, 2x6s, or other standard dimensional lumber by the piece | Linear feet (per piece) | Sold by length at fixed cross-sections |
| Buying random-width hardwood from a yard | Board feet | Widths vary, BF is the only fair comparison |
| Estimating a cabinet or furniture project | Board feet | Mixed sizes require volume accounting |
| Comparing prices between two species of hardwood | Board feet | Standardizes across width variations |
| Calculating a fence cost (pickets, rails, posts) | Linear feet | Fixed cross-sections sold by length |
| Buying rough-sawn lumber from a mill | Board feet | Mills sell all lumber in BF |
| Building a deck (joists, decking, rails) | Linear feet (mostly) | Standard dimensional softwoods |
| Buying live edge slabs or specialty hardwood | Board feet | Each piece has unique dimensions |
The general rule: if the lumber is sold in fixed standard cross-sections (2×4, 2×6, trim profiles), linear feet works. If the lumber varies in cross-section (random-width hardwoods, rough-sawn, slabs), board feet is required.
Need to run the numbers? Open the board foot calculator, plug in your dimensions, and see both per-piece and total BF instantly.
Common mistakes that cost money
Mistake 1: Buying hardwood by linear feet without checking width. A 10-foot piece of 4/4 walnut at $8 per linear foot sounds reasonable until you realize the board is 12 inches wide, making it 10 BF at an effective $8 per BF. But if the board is only 4 inches wide, you are paying $8 per linear foot for 3.33 BF, which works out to $24 per BF effective. The same lumber sold by BF would have been priced honestly at $6 to $9 per BF. Always ask: am I being quoted by LF or BF?
Mistake 2: Estimating a furniture project in linear feet. If you need lumber to build a bookcase with shelves in three different widths (8 inch, 10 inch, 12 inch), pricing by linear feet means three different effective per-foot costs and a high risk of running short on the widest boards. Board feet normalizes this. Plan furniture and cabinetry in BF.
Mistake 3: Forgetting that BF uses nominal dimensions. Softwood 2x4s are calculated as 2 inches by 4 inches even though their actual surfaced size is 1.5 by 3.5 inches. Hardwood 4/4 is calculated as 1 inch thick even after surfacing to roughly 13/16 inch. Using actual dimensions in a BF calculation gives you a smaller number than what the supplier will invoice, leading to confusion at checkout.
Mistake 4: Not adding a waste factor. Both linear and board foot estimates need a waste allowance. Trim work typically needs 10 to 15 percent for miter cuts and defects. Furniture-grade hardwood needs 15 to 20 percent for jointing, planing, and defect avoidance. Buying exactly what your raw math says will leave you one trip short of the lumber yard.
Worked comparison: same project, both units
Let’s price a simple bookcase using both methods to see how the numbers compare.
Project: A bookcase requiring six pieces of 4/4 cherry, 8 feet long, 8 inches wide.
Linear feet calculation:
- 6 boards × 8 feet = 48 linear feet
- Quoted at $7 per linear foot (8-inch width pricing)
- Total: 48 × $7 = $336
Board feet calculation:
- BF per board = (1 × 8 × 8) / 12 = 5.33 BF
- Total = 6 × 5.33 = 32 BF
- Quoted at $10.50 per BF (typical cherry pricing)
- Total: 32 × $10.50 = $336
Same total, two different units. Where it matters: if the boards came in random widths instead of all 8 inches (which is normal for hardwood), the linear feet calculation breaks down because not all linear feet contain the same amount of wood. The BF calculation handles the variation cleanly.
Which industries use which unit
- Carpentry (rough framing, decking, fencing): linear feet
- Finish carpentry (trim, baseboards, casing): linear feet
- Cabinetmaking: board feet
- Furniture making: board feet
- Sawmilling: board feet
- Lumber yards (retail): both, depending on product
- Home centers (Home Depot, Lowe’s): linear feet for dimensional, often per-piece pricing
- Specialty hardwood dealers: board feet exclusively
Bottom line
If your project uses fixed cross-section lumber (2x4s, trim, fencing), linear feet works fine. If your project uses random-width hardwood, mixed sizes, or rough-sawn lumber, board feet is required for honest pricing and accurate ordering.
When in doubt, ask your supplier which unit they price in, then run the conversion. Buying 50 linear feet of 4/4 walnut when the supplier prices in BF can produce wildly different totals depending on the actual widths of the boards delivered.
For accurate BF calculations with waste and cost included, use the free board foot calculator. It handles any thickness, width, length combination and outputs both BF and total cost in seconds.
FAQs
Can I convert linear feet to board feet without knowing thickness and width?
No. The conversion requires both the thickness and width of the lumber. Linear feet measures length only, while board feet is a volume measurement that requires all three dimensions. Without thickness and width, you cannot calculate BF from LF.
Is 1 linear foot the same as 1 board foot?
Only if the lumber is 1 inch thick and 12 inches wide. For any other cross-section, the two values differ. A 1-foot piece of 1×6 is 1 linear foot and 0.5 board feet. A 1-foot piece of 2×12 is 1 linear foot and 2 board feet.
Why do lumber yards use different units for different products?
Standard dimensional lumber (2x4s, 2x6s, etc.) has consistent cross-sections, so linear feet is sufficient and easier for retail customers. Hardwoods come in random widths, so board feet is the only fair way to price them. Trim and molding have fixed profiles, so linear feet matches how they are cut and sold.
Which unit do home improvement stores use?
Home Depot, Lowe’s, and similar retailers typically price softwood dimensional lumber by the piece (with the linear length specified) and trim by the linear foot. They rarely sell hardwood, but when they do, it is usually per piece with dimensions listed, not in board feet. Specialty hardwood dealers and sawmills use board feet exclusively.
How do I avoid getting confused at the lumber yard?
Ask three questions before agreeing to a price: (1) Are you quoting in linear feet or board feet? (2) Are the dimensions nominal or actual? (3) Is the waste factor my responsibility or included? Getting clear answers up front prevents budget surprises.
Does the conversion formula work for metric measurements?
The standard formula BF = (LF × T × W) / 12 requires inches for thickness and width and feet for linear feet. For metric, convert dimensions to imperial first, since BF is a North American unit with no native metric equivalent. Outside North America, lumber is typically sold by cubic meter or by piece.