Board Feet to Square Feet Converter
Convert board feet to square feet (or reverse) by entering the thickness. Works for any lumber thickness.
Formula
Square Feet = Board Feet ÷ Thickness (in inches)
Why thickness matters: board feet measure volume. The same volume of thicker lumber covers less surface area.
Board Feet → Square Feet Conversion Table
Values by board feet amount and lumber thickness (nominal).
| Board Feet | 3/4" (3/4) | 4/4 (1") | 5/4 (1.25") | 6/4 (1.5") | 8/4 (2") | 10/4 (2.5") | 12/4 (3") |
|---|---|---|---|---|---|---|---|
| 10 BF | 13.33 SF | 10 SF | 8 SF | 6.67 SF | 5 SF | 4 SF | 3.33 SF |
| 25 BF | 33.33 SF | 25 SF | 20 SF | 16.67 SF | 12.50 SF | 10 SF | 8.33 SF |
| 50 BF | 66.67 SF | 50 SF | 40 SF | 33.33 SF | 25 SF | 20 SF | 16.67 SF |
| 100 BF | 133.33 SF | 100 SF | 80 SF | 66.67 SF | 50 SF | 40 SF | 33.33 SF |
| 200 BF | 266.67 SF | 200 SF | 160 SF | 133.33 SF | 100 SF | 80 SF | 66.67 SF |
| 500 BF | 666.67 SF | 500 SF | 400 SF | 333.33 SF | 250 SF | 200 SF | 166.67 SF |
| 1000 BF | 1333.33 SF | 1000 SF | 800 SF | 666.67 SF | 500 SF | 400 SF | 333.33 SF |
How to Convert Board Feet to Square Feet
Board feet measure volume. Square feet measure area. To bridge the two you need thickness:
Square Feet = Board Feet ÷ Thickness (in inches)So 100 board feet of 4/4 lumber (1" thick) covers exactly 100 square feet. The same 100 board feet in 8/4 (2" thick) only covers 50 square feet — double the thickness means half the coverage area.
For the reverse — converting square feet to board feet — multiply instead:
Board Feet = Square Feet × Thickness (in inches)Why This Conversion Matters
Hardwood lumber is sold by the board foot. Many projects specify coverage in square feet. The conversion comes up constantly in:
- Hardwood flooring — you order by the board foot, but your floor plan is in square feet. At 4/4 (1"), they're equal. At 3/4", you'll get more coverage per board foot than you might expect.
- Wood paneling and wainscoting — wall coverage is measured in SF; lumber is priced in BF.
- Deck boards — 5/4 cedar decking is common. 100 BF of 5/4 stock covers only 80 SF, not 100 SF.
- Veneer and shop lumber — thin stock covers far more area per board foot than thick stock.
Worked Examples
Example 1 — Hardwood floors: You're installing 4/4 (1") white oak floors. You bought 300 board feet. How many square feet will it cover?
300 BF ÷ 1" = 300 SF
Example 2 — Cedar decking: Your deck needs 480 SF of coverage in 5/4 (1.25") cedar. How many board feet?
480 SF × 1.25" = 600 BF
Example 3 — Walnut wall panels: You have 150 BF of 6/4 (1.5") walnut for paneling. How much wall area will it cover?
150 BF ÷ 1.5" = 100 SF
At 1 Inch Thick, Board Feet Equal Square Feet
When lumber is exactly 1 inch thick, board feet and square feet are numerically the same. This is because a board foot is defined as 1" × 12" × 12" — if you lay those boards flat, 1 BF covers exactly 1 SF of surface. Thicker lumber contains more volume in the same footprint, so it covers less area per board foot. Thinner lumber (like 3/4" finish stock) covers more area per board foot.
For detailed board foot calculations by size, see the board foot chart. To estimate project quantities with waste, use the Lumber Estimator.
How to Use This Converter
Select the conversion direction — BF → Square Feet when you know your board footage and want to find coverage area, or SF → Board Feet when you have a floor or wall area to cover and need to calculate how many board feet to buy.
Then enter your value and select a thickness from the preset buttons (3/4", 4/4, 5/4, 6/4, 8/4, 10/4, 12/4) or type any custom thickness. The result and formula update instantly. Use actual thickness for physical coverage calculations; use nominal thickness when cross-referencing with a lumber yard invoice.
Nominal vs Actual Thickness and Coverage
Because board feet are typically tallied using nominal dimensions, there is an important distinction when calculating physical coverage:
- A 4/4 board is tallied at 1" thick (nominal), but actual surfaced thickness is typically 13/16"–3/4". Using nominal: 100 BF covers 100 SF. Using actual (0.75"): 100 BF covers 133 SF.
- A 5/4 decking board is tallied at 1.25" nominal, but actual thickness is often 1 1/16"–1 1/8". The difference affects how much area 200 BF of decking will actually cover.
- Rule of thumb: use nominal thickness to verify invoices; use actual thickness to estimate physical coverage for layout and installation planning.
When planning a hardwood floor installation, order by nominal board feet (matching what the dealer sells) but calculate room coverage using actual thickness if your measurement is precise.
Common Applications
- Hardwood flooring: Convert your room's square footage to board feet to order the right quantity. At 4/4 (1"), SF and BF are equal. At 3/4" finished thickness, multiply SF by 0.75 to get BF needed.
- Wall paneling and wainscoting: Calculate wall area in SF, then multiply by the board thickness to get the BF to order. Add 15% for waste and cuts around outlets.
- 5/4 deck boards: Your deck plan is in SF. Multiply by 1.25 to convert to BF. Add 10–15% for end cuts and spacing.
- Thin veneer and shop lumber: 3/8" thick boards cover more area per board foot than 4/4 stock — the converter handles any custom thickness you enter.
Board Foot Calculator · BF to Linear Feet → · Lumber Estimator →
Frequently Asked Questions
How many square feet are in 100 board feet of 4/4 lumber?
100 square feet. At exactly 1 inch thick, board feet and square feet are numerically equal. The formula is SF = BF ÷ thickness, so 100 BF ÷ 1 = 100 SF.
How do I convert board feet to square feet for hardwood flooring?
Divide your board feet by the thickness in inches. For 4/4 flooring (1 inch thick), SF = BF. For 3/4-inch flooring, SF = BF ÷ 0.75. For 5/4 (1.25 inches), SF = BF ÷ 1.25.
How many board feet do I need to cover 200 square feet with 5/4 decking?
250 board feet. Multiply square feet by the thickness in inches: 200 SF × 1.25 = 250 BF.
Does board width affect the board feet to square feet conversion?
No. The conversion depends only on thickness — width is already baked into the board foot calculation. BF already accounts for width, so only thickness is needed to convert to square feet.
How do I use the BF to square feet converter?
Select the conversion direction (BF → SF or SF → BF), enter your value, then select or type the board thickness in inches. Common hardwood thicknesses like 4/4 (1"), 5/4 (1.25"), and 6/4 (1.5") are available as preset buttons. The result and formula update instantly.
What thickness should I use for nominal vs actual lumber?
For retail purchases where the lumber yard prices by nominal board feet, use the nominal thickness (e.g., 1" for 4/4, 1.25" for 5/4). For coverage calculations with surfaced lumber, use the actual finished thickness (e.g., 0.75" for S4S 4/4 stock, ~1.06" for S2S 5/4). Using nominal gives BF-to-SF ratios that match the invoice; using actual gives the true physical coverage.
Why does thicker lumber cover less area per board foot?
Because a board foot is a fixed volume (144 cubic inches). Thicker boards pack more volume into each square foot of surface. Double the thickness and you halve the surface coverage per board foot. A 2" (8/4) board covers half the floor area of a 1" (4/4) board for the same number of board feet — the extra thickness is going into depth, not spread.