Answer: Enter your values and the Lumber Calculator returns the exact result instantly — formula, worked example, and a plain-English explanation are included below the tool.
Board feet, pieces from linear feet, and cost
Enter the nominal thickness and width in inches, the board length in feet, the linear feet your project needs, and a price per board. The calculator returns board feet per board, how many boards to buy, total board feet, and a cost estimate — the numbers you need whether you're framing a wall or buying hardwood by the board foot.
Board feet is the standard lumber volume unit: one board foot is a piece 12 inches × 12 inches × 1 inch thick. The formula the calculator uses is BF = thickness(in) × width(in) × length(ft) ÷ 12. Pieces are counted as linear feet ÷ board length, rounded up, so you buy whole boards.
The table shows board feet per board for common dimensional lumber at 8-foot length, computed with the exact formula above. Note these are the nominal dimensions you order; actual surfaced dimensions are smaller (a nominal 2×4 actually measures about 1.5 × 3.5 inches), but board-foot math conventionally uses nominal sizes.
A 2×4×8 contains 2 × 4 × 8 ÷ 12 = 5.33 board feet. An eight-foot 1×6 contains 4 board feet, and a 2×12×8 contains 16.
With the defaults — 2×4 stock in 8-foot lengths, 100 linear feet needed — each board is 5.33 BF and the project takes ceil(100 ÷ 8) = 13 boards. Total volume: 13 × 5.33 = 69.3 board feet. At $6 per board the estimate is $78.
If your supplier quotes by the board foot instead of per board, divide: 69.3 BF at, say, $1.10/BF is about $76 — the calculator's per-board price field handles either convention once you know the board price equivalent.
| Nominal Size | BF per 8 ft | BF per 10 ft | BF per 12 ft |
|---|---|---|---|
| 1×4 | 2.67 | 3.33 | 4.00 |
| 1×6 | 4.00 | 5.00 | 6.00 |
| 1×8 | 5.33 | 6.67 | 8.00 |
| 2×4 | 5.33 | 6.67 | 8.00 |
| 2×6 | 8.00 | 10.00 | 12.00 |
| 2×8 | 10.67 | 13.33 | 16.00 |
| 2×12 | 16.00 | 20.00 | 24.00 |
Linear feet just measures length along the board — a 10-foot 1×2 and a 10-foot 2×12 are both 10 linear feet. Board feet multiplies in thickness and width, so the 2×12 contains twelve times the wood. Estimating by linear feet alone works only when all boards are the same size, which is exactly the scenario this calculator models.
For framing takeoffs, add 10–15% for waste, culls, and cutting errors by increasing the linear-feet input accordingly.
Lumber prices move with grade and species. Construction-grade framing lumber (SPF, southern yellow pine) is priced per thousand board feet at wholesalers and per board at retail; hardwoods are graded (FAS, Select, #1 Common) and sold by the board foot, which is where the BF figure from this calculator directly applies. Pressure-treated lumber for ground contact costs more than the same board untreated, and longer boards carry a per-board premium out of proportion to their length because they're harder to ship defect-free.
When checking a delivered bundle, count boards and multiply by the per-board BF from this calculator; the tally tag on factory bundles uses the same nominal-size math, so your numbers should match within rounding. For big framing takeoffs, run the calculator once per stock size (plates in 2×4, headers in 2×12, and so on) and add the results — the linear-feet field keeps each run honest.
Store lumber flat and dry before use and let it acclimate to the job site, especially for interior finish work, so boards don't shrink or cup after installation.
What is the board feet formula?
Board feet = thickness(in) × width(in) × length(ft) ÷ 12. A 2×4×8 works out to 2 × 4 × 8 ÷ 12 = 5.33 BF. One board foot equals 144 cubic inches of wood.
How many 2×4 boards are in 100 linear feet?
If you buy 8-footers: ceil(100 ÷ 8) = 13 boards, totaling 69.3 board feet. The calculator rounds up because suppliers sell whole boards.
Do I use nominal or actual lumber dimensions?
Use nominal — the size you order, like 2×4. Board-foot pricing conventionally uses nominal dimensions even though a surfaced 2×4 actually measures about 1.5 × 3.5 inches.
How much extra lumber should I buy?
Add 10–15% for framing waste, offcuts, and culls. Enter the inflated linear footage in the calculator (e.g., 110–115 instead of 100) to price the realistic order.
What's the difference between linear feet and board feet?
Linear feet is length only; board feet includes thickness and width. Ten linear feet of 1×2 is 1.67 BF while ten feet of 2×12 is 20 BF — same length, very different wood volume.