Board Feet to Square Feet Calculator
Board foot to square feet: square feet = board feet ÷ thickness in inches. Enter the thickness, then type board feet or square feet and the other fills in. Prices per board foot and per square foot convert the same way. Free, no sign-up.
1 square foot of 1″ lumber = 1 board foot.
Square feet = board feet ÷ 1; board feet = square feet × 1.
200 board feet of 1″ lumber is 200 square feet.
The formulas
Square feet = board feet ÷ T
Board feet = square feet × T
T is the thickness in inches. A board foot is the volume of a board 1 foot long, 1 foot wide and 1 inch thick (NIST Handbook 130, §2.12.1.1), so each square foot of face holds T board feet. Both formulas are that definition rearranged; they're derived, not quoted. There's no 12 in them: 12 only appears when length is in feet and width in inches, as in T × W × L ÷ 12.
Worked examples
- 200 board feet of 4/4 lumber: 200 ÷ 1 = 200 square feet.
- 240 board feet of 8/4: 240 ÷ 2 = 120 square feet.
- 200 square feet of 5/4 lumber: 200 × 1.25 = 250 board feet.
- 8/4 at $12.00 per board foot: $12.00 × 2 = $24.00 per square foot.
Which thickness to enter
Use the thickness the lumber is sold by. Softwood board measure uses the nominal size, fractions included, so a 1×6 counts as 1″ thick though it's 3/4″ dry (PS 20-25, §2.2 and Table 3). Rough hardwood uses its quarter thickness, 5/4 = 1-1/4″, measured before surfacing, and a hardwood board under 1″ counts as 1″ (NHLA rules, ¶16). Pick Hardwood or Softwood in the calculator to apply the right rule.
Hardwood also has surface measure, an area measurement: the full width in inches × the standard length in feet ÷ 12, rounded to the nearest whole square foot, a half rounding down (NIST Handbook 130, §2.12.1.4). Surfaced hardwood in stock widths may state its quantity in square feet when a thickness is stated (§2.12.3.1). Surface measure leaves out the thickness, so multiply it by the thickness to get board feet.
How much the boards actually cover
Softwood board measure uses the nominal width (PS 20-25, §2.2), but surfaced boards are narrower. The table gives the share of the nominal face a 1×N board covers and the board feet it takes to cover 100 square feet, from the dry widths in PS 20-25 Table 3. NIST Handbook 130 Table 2 lists the same minimum widths for surfaced hardwood stock widths, which are sold by linear foot, count or surface measure rather than board feet (§2.12.3.1). Tongue-and-groove and shiplap edges overlap, so they cover less again; the table doesn't include that.
| Board | Dry width | Face covered | BF per 100 sq ft |
|---|---|---|---|
| 1×4 | 3-1/2″ | 87.5% | 114.3 |
| 1×6 | 5-1/2″ | 91.7% | 109.1 |
| 1×8 | 7-1/4″ | 90.6% | 110.3 |
| 1×10 | 9-1/4″ | 92.5% | 108.1 |
| 1×12 | 11-1/4″ | 93.8% | 106.7 |
Square feet in common board-foot amounts
| Board feet | 4/4 1″ | 5/4 1-1/4″ | 6/4 1-1/2″ | 8/4 2″ | 12/4 3″ |
|---|---|---|---|---|---|
| 100 BF | 100 | 80 | 66.7 | 50 | 33.3 |
| 200 BF | 200 | 160 | 133.3 | 100 | 66.7 |
| 240 BF | 240 | 192 | 160 | 120 | 80 |
| 360 BF | 360 | 288 | 240 | 180 | 120 |
| 480 BF | 480 | 384 | 320 | 240 | 160 |
| 600 BF | 600 | 480 | 400 | 300 | 200 |
| 1,000 BF | 1,000 | 800 | 666.7 | 500 | 333.3 |
Board feet in common square footage
| Square feet | 4/4 1″ | 5/4 1-1/4″ | 6/4 1-1/2″ | 8/4 2″ | 12/4 3″ |
|---|---|---|---|---|---|
| 100 sq ft | 100 | 125 | 150 | 200 | 300 |
| 200 sq ft | 200 | 250 | 300 | 400 | 600 |
| 500 sq ft | 500 | 625 | 750 | 1,000 | 1,500 |
| 1,000 sq ft | 1,000 | 1,250 | 1,500 | 2,000 | 3,000 |
Under 1″ the two rules differ: hardwood counts as 1″, so its square feet equal its board feet; softwood keeps its nominal fraction, so 100 board feet of 1/2″ softwood is 200 square feet.
Need board feet from a board's length instead? Use the linear feet to board feet calculator. Buying for a project? The board foot calculator turns a finished cut list into the rough lumber to buy, and the how-to page explains board feet in more detail.
Board feet and square feet FAQ
How many square feet is a board foot?
Board feet ÷ thickness in inches: 1 square foot at 1 inch, 0.5 at 2 inches. That's derived from the definition, a board 1 ft × 1 ft × 1 in. (NIST Handbook 130, §2.12.1.1). Hardwood under 1 inch counts as 1 inch (NHLA ¶16); softwood keeps its nominal fraction, so a board foot of 1/2-inch softwood is 2 square feet (PS 20-25, §2.2).
How many board feet is 200 square feet?
Multiply by the thickness in inches: 200 square feet is 200 board feet at 1 inch (4/4), 250 at 1-1/4 inches (5/4), 300 at 1-1/2 inches (6/4) and 400 at 2 inches (8/4). Derived from the board-foot definition, not quoted from a source.
How much will 200 board feet cover?
200 square feet at 1 inch thick, 100 at 2 inches, on the size it's sold by. Surfaced boards are narrower: a 1×6 is 5-1/2 inches wide dry (PS 20-25, Table 3), so 200 board feet of 1×6 covers about 183 square feet of face, and less again with tongue-and-groove or shiplap edges, which overlap. Derived from the board-foot definition and those widths.
Why do some converters multiply by 12?
Usually because they treat board feet as cubic feet. A board foot is 144 cubic inches, one twelfth of a cubic foot (12 × 12 × 12 = 1,728 cubic inches), so dividing board feet by the thickness in feet gives 12 times too many square feet. Check any converter with one board 12 inches wide, 12 inches long and 1 inch thick: that's 1 board foot and 1 square foot (NIST Handbook 130, §2.12.1.1).
Is square footage the same as surface measure?
Nearly. Surface measure, an area measurement for hardwood lumber, is the full width in inches × the standard length in feet ÷ 12, rounded to the nearest whole square foot, a half rounding down (NIST Handbook 130, §2.12.1.4). It leaves out the thickness; multiply by the thickness in inches to get board feet. Surfaced hardwood in stock widths may state its quantity in square feet when a thickness is stated (§2.12.3.1).
How do I convert a price per square foot to a price per board foot?
Divide by the thickness in inches: $/BF = $/sq ft ÷ T. 2-inch (8/4) lumber at $24.00 per square foot is $12.00 per board foot; the other way, multiply. That's derived from the board-foot definition, not quoted from a source.
Sources
- National Institute of Standards and Technology. Handbook 130, Uniform Laws and Regulations: IV-B Method of Sale of Commodities. 2026. Used: §2.12.1.1 Board Foot: the volume of a board 1 ft long, 1 ft wide and 1 in. thick, or its equivalent (144 in³ of wood); §2.12.1.4 surface measure; §2.12.3.1 S4S stock widths: quantity by linear measure (surfaced width and thickness stated), by count (length, surfaced width and thickness stated) or by surface measure in square feet (thickness stated); §2.12.3.2 nominal sizes allowed when marked “nominal” or “nom” and the actual sizes or Table 2 are prominently displayed; Table 2 minimum surfaced sizes for kiln-dried hardwood lumber.
- National Institute of Standards and Technology. Voluntary Product Standard PS 20-25, American Softwood Lumber Standard. PS 20-25, January 2025. Used: §2.2 board measure computed from nominal size; Table 3 dry dressed sizes.
- National Hardwood Lumber Association. Rules for the Measurement & Inspection of Hardwood & Cypress. Effective January 1, 2023. Used: ¶14 standard thicknesses for surfaced (S2S) lumber; ¶16 board measure: standard thicknesses under 1 in. (thin stock) count as 1 in., measured before surfacing.