The formula to calculate the board feet of lumber is:

\[ BF = \frac{T \cdot W \cdot L}{12} \]

Where:

• \(BF\) is the number of board feet (bd-ft).
• \(T\) is the thickness of wood (in.).
• \(W\) is the width of wood (in.).
• \(L\) is the length of wood (ft).