Board feet for lumber from thickness, width and length — so hardwood quotes become comparable.
Board Foot Calculator
Inputs
Nominal size — a 2×4 is nominally 2 in, actually 1.5 in.
Results
Total board feet
53.33
bf = (thickness(in) × width(in) × length(ft)) ÷ 12
Calculated with BuildCalculators.com
A board foot is a volume unit for lumber: 144 cubic inches, or a piece one inch thick, twelve inches wide and one foot long. Hardwood and rough-sawn timber are sold this way, so the price you are quoted is meaningless until you know how many board feet you are buying.
The formula is simple. The trap is that softwood dimensions are nominal — a 2×4 is neither 2 nor 4 inches.
bf = (thickness(in) × width(in) × length(ft)) ÷ 12bf = (T × W × L in inches) ÷ 144total = bf per piece × quantitycost = total bf × price per bfThe formula multiplies inches by inches by feet, which is a mixed unit. Dividing by 12 converts the length from feet to the equivalent in the inch-based volume, giving the standard 144 cubic inch board foot. If all three dimensions are in inches, divide by 144 instead.
A softwood 2×4 measures 1.5 × 3.5 inches after drying and planing. Board feet for construction lumber are conventionally calculated on the nominal size — 2 × 4 — because that is how the trade prices it. Using actual dimensions gives a smaller and non-standard figure.
Hardwood thickness is quoted in quarters of an inch: 4/4 is one inch, 6/4 is one and a half, 8/4 is two. It is measured rough, before surfacing, so 4/4 lumber surfaced on two sides finishes around ¾ inch — you pay for the rough thickness.
Sheet goods like plywood and OSB are sold by the sheet, and mouldings and trim by the linear foot. Board feet are for solid lumber sold by volume, which is mostly hardwood, rough-sawn softwood and timbers.
Standard framing lumber, priced by the board foot.
53.33 board feet
Calculated on nominal 2 × 4. The actual milled size is 1.5 × 3.5 inches, which would give 3.5 bf per piece — but that is not how lumber is priced.
Hardwood bought rough from a lumber yard.
6.67 board feet
Hardwood is measured rough. Surfaced on two sides this board finishes about ¾ inch thick, but you pay for the full inch.
Deck joists.
240 board feet
A 2×6 at 12 ft is exactly 12 board feet — a useful sanity check, since thickness × width ÷ 12 equals one here.
Nominal softwood sizes.
| Size | Board feet per ft | 8 ft piece | 12 ft piece |
|---|---|---|---|
| 1×4 | 0.33 | 2.67 | 4.00 |
| 1×6 | 0.50 | 4.00 | 6.00 |
| 2×4 | 0.67 | 5.33 | 8.00 |
| 2×6 | 1.00 | 8.00 | 12.00 |
| 2×8 | 1.33 | 10.67 | 16.00 |
| 2×10 | 1.67 | 13.33 | 20.00 |
| 2×12 | 2.00 | 16.00 | 24.00 |
| 4×4 | 1.33 | 10.67 | 16.00 |
| Nominal | Actual (dry, surfaced) |
|---|---|
| 1×4 | 0.75 × 3.5 in |
| 1×6 | 0.75 × 5.5 in |
| 2×4 | 1.5 × 3.5 in |
| 2×6 | 1.5 × 5.5 in |
| 2×8 | 1.5 × 7.25 in |
| 2×10 | 1.5 × 9.25 in |
| 4×4 | 3.5 × 3.5 in |
| Quarter | Rough thickness | Surfaced 2 sides |
|---|---|---|
| 4/4 | 1 in | 13/16 in |
| 5/4 | 1.25 in | 1 1/16 in |
| 6/4 | 1.5 in | 1 5/16 in |
| 8/4 | 2 in | 1 3/4 in |
| 12/4 | 3 in | 2 3/4 in |
Board feet exist so that lumber of different dimensions can be priced consistently. Once you have the figure, quotes from different yards become directly comparable.
Construction-grade pine and fir typically run $3–$6 per board foot in 2026, though most retailers price framing lumber by the piece rather than by volume. Lumber prices are notably volatile.
Poplar around $4–$6 per board foot, oak $6–$10, walnut and cherry $10–$18, and figured or wide stock considerably more. Buying rough and surfacing yourself saves roughly 20–30%.
Add 15–20% on hardwood for defects, cutting and matching grain. Rough boards arrive with sapwood, checks and irregular edges, and none of that ends up in the finished piece.
Rough hardwood from a sawmill is dramatically cheaper per board foot than surfaced stock from a retailer. If you have a planer and a jointer, that gap is the main reason to own them.
A 2×4 is 1.5 × 3.5 inches, but board feet for construction lumber are calculated on the nominal 2 × 4. Using actual sizes gives a figure about 34% lower and will not match any supplier quote.
They are only equal for a nominal 1×12. A 12 ft 2×6 is 12 linear feet but also 12 board feet, which coincidentally matches — a 12 ft 2×12 is 12 linear feet and 24 board feet.
4/4 lumber is one inch rough and finishes around ¾ inch surfaced. You pay for the rough thickness, and a project designed around ¾ inch stock needs 4/4 boards, not ¾ inch ones.
Rough hardwood is sold as it comes off the mill, with checks, sapwood and wane. Fifteen to twenty percent over your net requirement is normal, and more for narrow or clear cuttings.
Plywood, OSB and MDF are sold by the sheet, not by volume. Board feet apply to solid lumber only.
A volume unit for lumber: 144 cubic inches, equal to a piece one inch thick, twelve inches wide and one foot long. Hardwood and rough-sawn timber are priced this way.
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2×4 at 8 ft is (2 × 4 × 8) ÷ 12 = 5.33 board feet. If all three dimensions are in inches, divide by 144 instead.
Nominal, for construction lumber. A 2×4 measures 1.5 × 3.5 inches actual, but board feet are conventionally calculated on 2 × 4 because that is how the trade prices it. Using actual sizes gives a figure about a third lower.
Thickness in quarters of an inch. 4/4 is one inch, 6/4 is one and a half, 8/4 is two. It is measured rough before surfacing, so 4/4 finishes around ¾ inch — but you pay for the full inch.
0.67 board feet per linear foot, so an 8 ft length is 5.33 board feet and a 12 ft length is 8.
Only for a nominal 1×12. For everything else they differ — a 12 ft 2×12 is 12 linear feet but 24 board feet.
15–20% over your net requirement. Rough boards arrive with sapwood, checks and irregular edges, and none of that ends up in the finished piece. Allow more for narrow or clear cuttings.
No. Sheet goods are sold by the sheet and trim by the linear foot. Board feet apply to solid lumber sold by volume.
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This calculator uses published constants from named industry sources, each asserted in an automated test that runs on every build. The formula is printed with the result above, and any correction we make is logged on the changelog.
It is a planning estimate. It does not replace an engineer, a site visit or a written quote — confirm quantities with your supplier before ordering.