Board Feet vs. Linear Feet: Lumber Pricing Explained and How Not to Overpay

The Confusion That Costs Contractors Money

Ask ten contractors the difference between a board foot and a linear foot, and you’ll get ten slightly different answers. Most understand the concept but can’t quickly articulate the math. And that’s when mistakes happen. A supplier quotes a price per linear foot; you estimate the quantity in board feet without converting; you bid the job at a loss; or worse, you get to the lumber yard and realize your takeoff was wrong.

Board feet and linear feet are different units for different purposes. Lumber suppliers use board feet for pricing and inventory. Carpenters often estimate in linear feet (also called running feet) because that’s how they naturally think about boards and beams on a structure. Confusing the two is one of the fastest ways to blow a material estimate.

What Is a Board Foot?

A board foot is a standardized unit of lumber volume. It’s exactly 144 cubic inches: a board 12 inches long, 12 inches wide, and 1 inch thick.

In a standard 2×4, the actual dimensions are closer to 1.5 × 3.5 inches. An 8-foot 2×4 contains:

Length: 8 feet = 96 inches
Width: 3.5 inches
Thickness: 1.5 inches
Volume: 96 × 3.5 × 1.5 = 504 cubic inches

Converting to board feet: 504 ÷ 144 = 3.5 board feet

The formula: Board Feet = (Length × Width × Thickness) ÷ 12

Where length is in feet, and width and thickness are in inches.

For that 8-foot 2×4:

Length: 8 feet
Width: 4 inches
Thickness: 2 inches (nominal)

Board Feet = (8 × 4 × 2) ÷ 12 = 64 ÷ 12 = 5.33 board feet

Wait—why is that different from 3.5? Because the “2” and “4” in “2×4” are nominal sizes, not actual sizes. The actual thickness is 1.5 inches and actual width is 3.5 inches.

For board foot calculations, always use nominal dimensions, which is what the lumber is labeled as:

2×4 = 2 inches thick, 4 inches wide
2×6 = 2 inches thick, 6 inches wide
2×8 = 2 inches thick, 8 inches wide
1×12 = 1 inch thick, 12 inches wide

What Is a Linear Foot?

A linear foot (or running foot) is simply a length measurement: 12 inches along the length of a board. It ignores width and thickness.

If you estimate “I need 240 linear feet of 2×6,” you’re saying: “I need 240 feet of board stock, 6 inches wide and 2 inches thick, total thickness unspecified.”

Converting Linear Feet to Board Feet

This is where contractors lose money.

Formula: Board Feet = Linear Feet × (Width in inches ÷ 12) × (Thickness in inches ÷ 12)

Actually, here’s the simpler way:

Board Feet = (Linear Feet × Nominal Width × Nominal Thickness) ÷ 12

Example 1: Convert 240 linear feet of 2×6 to board feet

Board Feet = (240 × 6 × 2) ÷ 12 = 2,880 ÷ 12 = 240 board feet

Interesting: for 2-inch thick lumber, linear feet numerically equals board feet if you use the nominal width. 240 linear feet of 2×6 = 240 board feet.

Example 2: Convert 100 linear feet of 1×12 to board feet

Board Feet = (100 × 12 × 1) ÷ 12 = 1,200 ÷ 12 = 100 board feet

Again, 1-inch thick lumber: linear feet = board feet (for the nominal width).

Example 3: Convert 150 linear feet of 4×8 to board feet

Board Feet = (150 × 8 × 4) ÷ 12 = 4,800 ÷ 12 = 400 board feet

This one’s very different. Thicker, wider boards accumulate board feet quickly. 150 linear feet of 4×8 is a lot of volume.

Why Suppliers Use Board Feet

Board feet standardize pricing regardless of width or thickness. A 2×6 and a 2×8 cost different amounts per board foot, but both are priced per board foot, not per linear foot. This keeps the system consistent.

If suppliers priced per linear foot, they’d have to maintain separate prices for every width:

2×4 per linear foot
2×6 per linear foot
2×8 per linear foot
Etc.

By pricing per board foot, a single price applies to all products of the same species and grade.

The Real-World Scenario Where Contractors Lose Money

You’re estimating a large deck project:

Your takeoff says:

Pressure-treated 2×6 rim joist: 140 linear feet
Pressure-treated 2×8 joists: 320 linear feet
Pressure-treated 2×6 decking: 1,200 linear feet

You call a supplier for a quote. They ask for the quantity in board feet.

You haven’t done the conversion. You either:

Eyeball it and guess: “About 800 board feet?” (Wrong—it’s much more.)
Give them linear feet: “140 of 2×6, 320 of 2×8, 1,200 of 2×6 decking.” (They have to convert, and you lose the conversation if they get busy or move on to another customer.)
Do the math correctly: Convert everything to board feet and give them a solid number.

The correct calculation:

Rim joist: (140 × 6 × 2) ÷ 12 = 140 board feet Joists: (320 × 8 × 2) ÷ 12 = 426.67 board feet Decking: (1,200 × 6 × 2) ÷ 12 = 1,200 board feet

Total: 1,766.67 board feet

If lumber is $0.85 per board foot, that’s $1,501 in materials.

If you’d guessed 800 board feet, you’d think the cost was around $680—nearly $800 off on a single material line item. Your bid is too low, and you’re eating the difference.

Lumber Grade and Species Affect Price

Board feet gives you volume, but pricing varies by:

Species: Douglas fir, Southern pine, hemlock, cedar, etc. Each has different cost structures.
Grade: Premium (clear, no knots), Select, No. 1, No. 2, Utility, etc. Lower grades cost less.
Treatment: Pressure-treated (outdoor use) costs more than untreated. Ground-contact treatment (for posts or beams touching soil) costs even more.
Moisture content: Kiln-dried (KD) is generally cheaper than green (freshly cut). Pressure-treated lumber is often sold green because the treatment process uses moisture.

Don’t assume all 2×6s cost the same. A pressure-treated 2×6 for exterior use might be $1.20/BF, while a clear cedar 2×6 could be $3.50/BF or higher.

Common Mistakes in Lumber Estimates

Confusing nominal and actual dimensions when calculating board feet. Always use nominal sizes (what’s printed on the label), not actual sizes (what you measure). 2×4 = 2 and 4 in the formula, not 1.5 and 3.5.

Forgetting waste factor. Lumber estimates should include 5–10% for waste (kerf loss from cutting, damaged boards, returns for splitting). If your calculated requirement is 1,000 board feet, order 1,050–1,100.

Mixing price per linear foot with price per board foot. Some specialty lumber or molding might be quoted per linear foot (especially trim or hardwood). Confirm the unit with the supplier before comparing prices.

Not accounting for different dimensions in the same project. A deck has multiple lumber types (rim joist, band boards, joists, decking, railings, etc.). Each must be converted to board feet separately.

Underestimating decking waste. Deck boards are often not full-width usable due to edge defects or knots. Plan 10–12% waste for decking specifically.

The Fast Way to Calculate

Our board feet calculator handles the conversion instantly. Enter:

Linear feet needed
Nominal width and thickness
Quantity of different sizes

Get a board feet total, and you’re ready to call the supplier with confidence.

For complex projects with multiple lumber sizes, create a simple spreadsheet:

Lumber Type	Linear Feet	Width	Thickness	Board Feet
2×6 joists	320	6	2	426.67
1×12 boards	240	12	1	240
4×8 beams	50	8	4	133.33
TOTAL				800

Add a waste factor (10%), and you have 880 board feet to order.

The Bottom Line

Board feet and linear feet serve different purposes. Linear feet is what you measure on the structure; board feet is what suppliers price. Knowing how to convert between them is as essential as knowing how to read a tape measure. Get this right, and your material estimates will be accurate. Mess it up, and you’ll either overbid and lose the job or underbid and lose money.