Lumber Calculator
Home & ConstructionCalculate board feet and lumber cost for decks, framing, joists, fencing, and other construction projects.
Lumber Sizing Guide
| Nominal Size | Actual Size | Common Uses |
|---|---|---|
| 2×4 | 1.5″ × 3.5″ | Framing, studs, posts |
| 2×6 | 1.5″ × 5.5″ | Deck boards, joists |
| 2×8 | 1.5″ × 7.25″ | Floor/roof joists |
| 2×10 | 1.5″ × 9.25″ | Large spans, beams |
| 1×4 / 1×6 | 0.75″ × 3.5/5.5″ | Pickets, trim, sheathing |
Standard Lumber Spacing
| Application | Typical Spacing | Notes |
|---|---|---|
| Wall Studs | 16″ on center | Standard residential |
| Floor Joists | 16″ on center | Typical residential spans |
| Roof Rafters | 16″ or 24″ | 24″ if 2×8 or larger |
| Deck Boards | 16″ on center | 2×6 or 2×8 boards |
| Fence Pickets | 4″–6″ | Varies by aesthetic |
How to Use This Calculator
- Select your project type (deck, framing, joists, or fence)
- Enter length and width in feet
- Specify spacing (typically 12″, 16″, or 24″)
- Choose lumber size (2×4, 2×6, etc.)
- Enter current lumber cost per board foot
- Get instant board feet and cost estimate
Frequently Asked Questions
How do I calculate board feet for a deck?
For a deck, measure the length and width in feet, then decide on joist/board spacing (typically 16 inches). Use the formula: (Number of boards × length × width in inches ÷ 12). For example, a 12×10 ft deck with 2×6 boards 16 inches apart needs roughly 120 board feet. This calculator does it automatically.
What's the difference between nominal and actual lumber sizes?
Nominal size is what lumber is sold as (2×4, 2×6, etc.). Actual size is smaller: a 2×4 is really 1.5×3.5 inches, a 2×6 is 1.5×5.5 inches. A 2×8 is 1.5×7.25 inches. Always use actual dimensions for accurate board foot calculations. This affects strength calculations and spacing.
How much spacing should I use for joists or studs?
Common spacing: 12 inches (tighter, more support). 16 inches (standard for residential). 24 inches (maximum for most applications). Closer spacing = more lumber needed but better support. Building codes specify minimum spacing based on joist size and load. Always check local codes for your project.
How do I calculate lumber for framing walls?
For wall framing: measure wall length in feet, assume 8 ft wall height. Studs are typically 2×4 or 2×6 spaced 16 inches apart. Calculate: (wall length ÷ 1.33) = number of studs. Multiply by stud length and board foot value. Include top and bottom plates. This calculator estimates the total for you.
What is the cost of lumber per board foot?
Lumber prices vary by type and market: Softwood 2×4/2×6: $1.00–$2.50/BF. Treated lumber: $1.50–$3.50/BF. Hardwood: $3.00–$8.00/BF. Prices fluctuate based on supply. Check local lumber yards for current pricing. This calculator lets you enter your regional prices for accurate estimates.
How do I calculate lumber needed for a fence?
Fence calculation: measure total length in feet, decide on picket spacing (typically 5–6 inches). A 6 ft fence section with 5 inch spacing needs about 14–15 pickets. For 100 ft of fence at 6 inch spacing: roughly 200 linear feet of 1×4 pickets = about 67 board feet. Add posts every 6 ft.