What Are Board Feet?
Board feet measure the volume of lumber—not just length like linear feet, or area like square feet. Think of it as "how much wood" you're actually buying.
1 board foot = 144 cubic inches = a piece 1" thick × 12" wide × 12" long
The Board Feet Formula
Master Formula
Board Feet = (Thickness × Width × Length) ÷ 12
Units: Thickness & Width in INCHES, Length in FEET
Alternative Formula (All Inches):
Board Feet = (Thickness × Width × Length) ÷ 144
Use this when all measurements are in inches
Step-by-Step Calculation Guide
Step 1: Measure Thickness
Measure in inches. For a 2×4, use the nominal size: 2 inches (not the actual 1.5")
Step 2: Measure Width
Measure in inches. For a 2×4, use 4 inches (not the actual 3.5")
Step 3: Measure Length
Measure in feet. An 8-foot board = 8 feet
Step 4: Apply Formula
Multiply thickness × width × length, then divide by 12
Step 5: Multiply by Quantity
If buying multiple pieces, multiply by the number of pieces
Real-World Examples
Example 1: Standard 2×4×8
Given: One 2×4 that's 8 feet long
Thickness: 2 inches
Width: 4 inches
Length: 8 feet
Board Feet = (2 × 4 × 8) ÷ 12 = 64 ÷ 12 = 5.33 BF
Result: 5.33 board feet
Example 2: Hardwood Plank
Given: Oak plank 1.25" thick × 6" wide × 10 feet long
Thickness: 1.25 inches
Width: 6 inches
Length: 10 feet
Board Feet = (1.25 × 6 × 10) ÷ 12 = 75 ÷ 12 = 6.25 BF
Result: 6.25 board feet
Example 3: Multiple Pieces
Given: 10 pieces of 1×6×12 pine boards
Per piece: (1 × 6 × 12) ÷ 12 = 6 BF
Total pieces: 10
Total Board Feet = 6 BF × 10 pieces = 60 BF
Result: 60 board feet total
Common Lumber Sizes & Board Feet
| Lumber Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1×4 | 2.67 BF | 3.33 BF | 4.0 BF | 5.33 BF |
| 1×6 | 4.0 BF | 5.0 BF | 6.0 BF | 8.0 BF |
| 2×4 | 5.33 BF | 6.67 BF | 8.0 BF | 10.67 BF |
| 2×6 | 8.0 BF | 10.0 BF | 12.0 BF | 16.0 BF |
| 2×8 | 10.67 BF | 13.33 BF | 16.0 BF | 21.33 BF |
Calculating Lumber Costs
Cost Formula
Total Cost = Board Feet × Price per Board Foot
Example Cost Calculation
Project: 20 pieces of 2×4×8 pine
Board feet per piece: 5.33 BF
Total board feet: 20 × 5.33 = 106.6 BF
Price per BF: $0.65
Total Cost = 106.6 BF × $0.65 = $69.29
Project cost: $69.29 (plus tax)
Common Board Feet Mistakes to Avoid
❌ Using Actual vs Nominal Dimensions
Wrong: 2×4 = 1.5" × 3.5" (actual size)
Right: 2×4 = 2" × 4" (nominal size for BF calculations)
❌ Wrong Units
Remember: Thickness and width in inches, length in feet. Don't mix units or your calculation will be way off.
❌ Confusing Linear and Board Feet
Linear feet = length only. Board feet = volume (length × width × thickness). They're completely different measurements.
❌ Forgetting Multiple Pieces
Calculate BF for one piece first, then multiply by quantity. Don't forget this step when buying multiple boards.
Pro Tips for Board Feet Calculations
Quick Mental Math:
- • 2×4×8 = roughly 5⅓ BF
- • 1×6×12 = exactly 6 BF
- • Double the length = double the BF
- • Remember: 12 × 12 × 1 = 144 cubic inches = 1 BF
Buying Tips:
- • Buy 10% extra for waste and mistakes
- • Check lumber grade vs price
- • Compare BF prices between species
- • Consider buying longer lengths to minimize waste
Master Board Feet Calculations
- • Formula: (Thickness × Width × Length) ÷ 12
- • Units matter: inches for T&W, feet for length
- • Use nominal dimensions (2×4, not 1.5×3.5)
- • Board feet = volume, not length or area
- • Practice makes perfect - use our calculator to check your math!