Lumber Calculator
Calculate board feet from board dimensions, or find how many boards you need to cover a deck, floor, or fence.
Calculation type
Actual width, e.g. 5.5 for 2×6
Actual thickness, e.g. 1.5 for 2×
Actual width, e.g. 5.5 for 2×6
0.25″ is standard for decking
Results
Board Feet
—
board feet total
Per Board
—
board feet each
Linear Feet
—
total linear ft
How to Calculate Board Feet
A board foot is a unit of lumber volume equal to 1 foot wide, 1 foot long, and 1 inch thick (144 cubic inches). It accounts for both the size and quantity of lumber, making it the standard unit for pricing and ordering.
Formula: Board Feet = (Thickness in × Width in × Length in) ÷ 144. Or equivalently: Length ft × Width in × Thickness in ÷ 12.
Common Lumber Sizes — Nominal vs. Actual
| Nominal Size | Actual Size | Common Use |
|---|---|---|
| 2×4 | 1.5″ × 3.5″ | Framing, studs |
| 2×6 | 1.5″ × 5.5″ | Decking, joists |
| 2×8 | 1.5″ × 7.25″ | Joists, rafters |
| 2×10 | 1.5″ × 9.25″ | Beams, headers |
| 1×6 | 0.75″ × 5.5″ | Fence boards, trim |
| 1×4 | 0.75″ × 3.5″ | Trim, furring |
Frequently Asked Questions
- What is the difference between board feet and linear feet?
- Linear feet measures only length, ignoring width and thickness. Board feet measures volume — it factors in all three dimensions. Lumber is priced in board feet; length-only materials like trim are priced in linear feet.
- Why do nominal and actual lumber sizes differ?
- Lumber is sized before drying and surfacing. A 2×4 starts at 2 inches by 4 inches but shrinks and is planed smooth during milling, ending up at 1.5″ × 3.5″. Always use actual dimensions when calculating.
- How much extra lumber should I buy?
- Adding 10% for waste and cut-offs is standard for most projects. For diagonal or pattern layouts (like herringbone decking), add 15–20% to account for additional angled cuts.