Volume ↔ area
Board Feet to Square Feet Calculator
Convert board feet to square feet (and back) once you know the thickness — board feet measure volume, square feet measure area. New to the math? See how to calculate board feet.
How do you convert board feet to square feet?
Square feet = board feet ÷ thickness (in). The reverse is board feet = square feet × thickness (in). For one-inch (4/4) stock the two numbers are equal, which is why 4/4 lumber is easy to picture: 1 board foot of 1-inch wood covers exactly 1 square foot.
Worked example
You have 20 board feet of 6/4 (1.5 in) walnut. Square feet of face = 20 ÷ 1.5 = 13.33 sq ft. The same 20 board feet in 4/4 (1 in) stock would cover 20 sq ft — thinner wood spreads the same volume over more area. The calculator does the arithmetic instantly so you can match a slab's face area to the board feet you bought.
If you actually need length rather than area, use the board feet to linear feet calculator instead.
| Thickness | Call | Square feet |
|---|---|---|
| 1.00″ | 4/4 | 20.00 |
| 1.25″ | 5/4 | 16.00 |
| 1.50″ | 6/4 | 13.33 |
| 2.00″ | 8/4 | 10.00 |
How do you convert square feet to board feet?
Board feet = square feet × thickness (in). It is the same relationship read from the other end, and it is the one that matters when you are standing at the yard with a plan view rather than a pile of lumber. A square foot to board foot conversion needs exactly one extra number — the thickness you intend to mill to — because area alone cannot describe volume.
Worked example: a wall of shelving that covers 24 square feet of face, built from 5/4 (1.25″) white oak, is 24 × 1.25 = 30 board feet of clean stock before waste. Run the identical 24 sq ft at 6/4 (1.5″) and the order becomes 36 BF; at 8/4 it is 48 BF. Same surface, three different invoices, which is why dealers never price by the square foot.
| Face area | at 4/4 (1″) | at 6/4 (1.5″) | at 8/4 (2″) |
|---|---|---|---|
| 10 sq ft | 10 BF | 15 BF | 20 BF |
| 20 sq ft | 20 BF | 30 BF | 40 BF |
| 24 sq ft | 24 BF | 36 BF | 48 BF |
| 40 sq ft | 40 BF | 60 BF | 80 BF |
Skip the arithmetic and go straight from dimensions to footage with the cut list calculator, which totals every part on the drawing and hands you one board-foot number to bring back here.
Why do you need thickness to convert?
This trips up customers at my counter constantly: they hand me a square-foot number for a tabletop and expect a board-foot price, but I can't quote without the thickness. A board foot is a volume; a square foot is only area. The same 20 board feet covers 20 sq ft at 1 inch but just 10 sq ft at 2 inches — double the thickness, half the face. Skip the thickness and the conversion is meaningless, which is exactly why this tool asks for it before it answers.
When do woodworkers actually need this conversion?
I use it for tabletops, butcher-block counters, and glued-up panels where the plan shows square feet but the invoice is in board feet. A 3 ft × 6 ft tabletop is 18 sq ft of face, so at 8/4 (2″) stock the rule above gives 18 × 2 = 36 board feet before waste. Add the waste factor from the waste factor guide, then buy.
Sheet goods reverse the problem: plywood is sold by the sheet (area), not by board feet. Do not run plywood through this converter and expect a lumber-yard BF price to match.
Quote board feet when you're buying solid lumber by volume; quote square feet when you're covering a surface. The conceptual split belongs to board feet vs square feet — this page is only the arithmetic bridge between the two.
Frequently asked questions
How do you convert board feet to square feet?
Square feet equals board feet divided by thickness in inches. For 10 board feet of 1-inch stock that is 10 ÷ 1 = 10 square feet, and for 1.5-inch stock it is 10 ÷ 1.5 = 6.67 square feet.
Why do I need thickness to convert?
Board feet measure volume and square feet measure area, so you must know thickness to move between them. The same 10 board feet covers twice the area at half the thickness.
How do you convert square feet to board feet?
Multiply square feet by the thickness in inches. Covering 24 square feet with 5/4 (1.25-inch) stock is 24 × 1.25 = 30 board feet; the same area in 8/4 (2-inch) stock is 48 board feet. Switch the calculator to “square feet → board feet” to do it instantly.
Is one board foot always one square foot?
Only for one-inch (4/4) stock. At 1 inch thick, 1 board foot equals 1 square foot of face. Thicker stock yields fewer square feet per board foot, so 6/4 (1.5-inch) wood gives about 0.67 square feet per board foot.