Board Feet Calculator
Calculate board feet (BF) from thickness, width, and length in inches or cm.
Includes the board foot formula, standard lumber sizes, and total cost estimate.
Lumber quantity for framing projects is calculated based on linear feet of framing members needed, converted to board count for your chosen lumber size.
Board Foot Formula (for pricing):
Board Feet = (Thickness in × Width in × Length ft) / 12
Stud Count Formula (wall framing):
Studs = (Wall Length ft / Stud Spacing ft) + 1
Add 1 because you need a stud at both ends. For 16-inch OC spacing, divide by 1.333; for 24-inch OC, divide by 2.
Worked example — framing a 20-foot wall: 16-inch on-center spacing: Studs = (20 / 1.333) + 1 = 15 + 1 = 16 studs Add 3 extra for corners, blocking, and headers → order 19 studs
Each stud is typically an 8-foot 2×4 or 2×6.
Board feet in common lumber sizes:
| Size | Length | Board Feet |
|---|---|---|
| 2×4 | 8 ft | 5.33 BF |
| 2×4 | 12 ft | 8.0 BF |
| 2×6 | 8 ft | 8.0 BF |
| 2×8 | 10 ft | 13.3 BF |
Standard waste factors to add:
- Wall framing: 10–15%
- Roof rafters: 15–20% (cuts and angles)
- Decking/flooring: 10% for straight runs, 15% for diagonal
Lumber grades for common uses:
- Structural framing: #2 or better (most code-compliant uses)
- Appearance framing (visible): Select Structural or #1
- Decking: Pressure-treated (ground contact rated for below-grade)
- Interior trim: Clear or finger-jointed pine (paintable)
Always check local building codes for minimum lumber grades in load-bearing applications.