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.
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.
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.
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.