CSLB General Building (B)Planning and EstimatingMedium
A carpenter needs to order lumber for 20 pieces of 2x8 boards, each 12 feet long. Using the standard board foot formula, how many board feet of lumber are required?
- A400 board feet
- B320 board feet
- C160 board feet
- D240 board feet
Show answer & explanationAnswer & explanation
Correct answer: B. 320 board feet
Board feet per piece = (Thickness in inches x Width in inches x Length in feet) / 12 = (2 x 8 x 12) / 12 = 16 board feet per piece. For 20 pieces: 16 x 20 = 320 board feet.
Why the other options are wrong
- A. This overestimates the total by using the wrong divisor.
- C. This underestimates the per-piece board footage.
- D. This result comes from an incorrect formula application.
Board Foot Calculation
A board foot is a unit of lumber volume equal to a piece 12 inches x 12 inches x 1 inch, calculated as (Thickness x Width x Length)/12.
- Thickness and width are in inches, length is in feet
- Divide by 12 to convert to board feet
- Lumber is typically priced and ordered by board foot
Memory trick: Thickness times width times length, then divide by twelve to get your bill.