Volume vs length
Board Feet vs Linear Feet
A linear foot is just one foot of length, no matter how wide or thick the board is. A board foot is a volume. So two sticks can have identical linear feet but wildly different board feet — which is exactly why dealers pick one unit over the other, and why it pays to calculate board feet before you trust a per-foot price.
| Board feet | Linear feet | |
|---|---|---|
| Measures | Volume of wood | Length only |
| Cares about width/thickness? | Yes | No |
| Formula | T × W × L(ft) ÷ 12 | Just the length in feet |
| Used for | Hardwood, rough stock | Trim, molding, dimensional softwood |
What's the difference between board feet and linear feet?
A linear foot answers one question: how long is the piece? It says nothing about how wide or thick the board is. A board foot answers a different question: how much wood is in the piece? It folds thickness, width, and length into a single volume. Two boards can run the same number of linear feet and still hold completely different amounts of wood.
Take 8 linear feet of 1×4 and 8 linear feet of 1×12. Same length, same linear feet — but the 1×12 is three times as wide and therefore three times the board feet: 1 × 4 × 8 ÷ 12 = 2.67 BF for the narrow board versus 1 × 12 × 8 ÷ 12 = 8 BF for the wide one. Pay by linear foot and the wide board is a steal; pay by board foot and you pay for exactly what you carry out.
How do you convert linear feet to board feet?
The trick is that a fixed cross-section has a fixed board-feet-per-linear-foot value, so you only compute it once:
BF per linear foot = thickness (in) × width (in) ÷ 12
Worked example with a known cross-section: you're quoted 40 linear feet of 4/4 (1″) cherry that runs a consistent 6″ wide. BF per foot = 1 × 6 ÷ 12 = 0.5. Total = 0.5 × 40 = 20 board feet. Bump that cross-section to 8/4 × 8″ and the per-foot value jumps to 2 × 8 ÷ 12 = 1.33, so the same 40 linear feet is now 53.3 board feet — more than double, with not one extra foot of length. The board feet to linear feet calculator runs this in both directions when you know thickness and width.
When is lumber sold by each unit?
Trim, molding, dowels, and flooring planks have a fixed, milled cross-section, so length alone defines the quantity — linear feet (or "lineal feet" on some price lists) are simple and fair. Hardwood comes in random widths straight off the log, so only volume in board feet compares one board honestly against another. Dimensional softwood sits in the middle: a 2×4 is always a 2×4, so it's often sold per piece or per linear foot even though it could be priced by volume.
This is why the home center sells you a stick of casing by the foot but a hardwood dealer hands you a board-foot tally. The cross-section is either standardized or it isn't, and that single fact decides the unit. If you also need the area-based comparison for coverage work, see board feet vs square feet.
Why should you convert competing quotes to board feet?
I once had two suppliers bid the same white oak job, one quoting per linear foot on random-width boards and the other quoting per board foot. On paper the linear-foot price looked 15% cheaper. But the linear-foot stock averaged narrower, so once I converted both to board feet, the "cheap" quote was actually the more expensive wood per unit of volume.
In my experience, mixing linear and board feet on random-width hardwood quietly skews a comparison by 10–20% — that's my own estimate from years of bid sheets, not a published figure, and it swings with how wide the boards run. The habit that saves the money is mechanical: reduce every quote to board feet before you compare, because volume is the only apples-to-apples basis for solid lumber. My pre-order routine for exactly this is in how to buy lumber by board foot.
If a quote switches units between two suppliers, convert both to board feet first. It's the only apples-to-apples basis for solid lumber, and it's the fastest way to catch a price that looks cheap but isn't.
Frequently asked questions
What is the difference between board feet and linear feet?
A linear foot is one foot of length regardless of width or thickness, while a board foot measures volume using thickness, width, and length. Two boards can be the same linear feet but very different board feet.
Why is trim sold by linear foot but hardwood by board foot?
Trim and molding have a fixed profile, so length alone defines the quantity and linear feet work well. Hardwood boards vary in width, so volume in board feet is the only fair common unit.
How do I convert linear feet to board feet?
Find the board feet in one linear foot of that cross-section — thickness × width ÷ 12 — then multiply by total linear feet. A 1″ × 6″ board is 0.5 BF per linear foot, so 8 linear feet is 4 board feet.