How Much Lumber Do I Need?

The amount of lumber you need depends on the project type and lumber dimensions. Here's how to calculate board feet and estimate quantities for common DIY projects.

The board feet formula

Board feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12

Board foot is the standard unit for buying lumber in the US. One board foot = 1 inch thick × 12 inches wide × 12 inches long.

Common lumber sizes — actual vs nominal

Nominal size	Actual size	Board feet per 8’ piece
1×4	0.75” × 3.5”	2.67 bf
1×6	0.75” × 5.5”	4.00 bf
2×4	1.5” × 3.5”	5.33 bf
2×6	1.5” × 5.5”	8.00 bf
2×8	1.5” × 7.25”	10.67 bf
2×10	1.5” × 9.25”	13.33 bf
4×4	3.5” × 3.5”	10.67 bf

How to estimate lumber for common projects

Framing a wall (16” on center)

Wall length ÷ 1.33 = number of studs
Add 1 stud per corner + 1 per door/window opening
Add 3 plates: 2× bottom plate + 1× top plate (all = wall length × 3)
Add 10–15% waste

Example: 10-foot wall → 8 studs + 30 linear feet of plate lumber

Decking

Area (sq ft) × 1.15 for 10% waste + spacing gaps
Divide by the width of your deck boards to get the linear feet needed

Fencing (6-ft privacy fence)

Number of panels × 7 boards per panel (for 6” boards)
Add posts every 8 feet: (total length ÷ 8) + 1

Quick project estimates

Project	Typical lumber needed
8×8 ft shed	200–300 board feet
12×16 ft deck	400–600 board feet
8-ft fence (100 lin ft)	500–700 board feet
Single door frame	20 board feet
Interior wall (10 ft)	50–70 board feet

Add 10–15% for waste on all projects.

Tips for buying lumber

Buy in bulk for larger projects — lumber yards offer better per-board-foot pricing than big-box stores for 20+ pieces.
Check for pressure-treated lumber for any outdoor or ground-contact use.
Let lumber acclimate — store indoors 48–72 hours before use to minimize warping.

Frequently Asked Questions

How do I calculate board feet of lumber?

Board feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12. For example, a 2×4 that is 8 feet long = (2 × 4 × 8) ÷ 12 = 5.33 board feet.

How much lumber do I need for a deck?

For a simple deck, multiply the deck area by 1.15 to account for waste and joist spacing. A 12×16 ft deck (192 sq ft) needs roughly 220 board feet of decking plus framing lumber for the structure.

What is the difference between nominal and actual lumber size?

Nominal size is the name (e.g., 2×4), while actual size is smaller after milling and drying. A nominal 2×4 is actually 1.5" × 3.5". Always use actual dimensions when calculating coverage.

How many 2x4s do I need for a wall?

A standard 8-foot wall needs one 2×4 every 16 inches on center. For a 12-foot long wall: 12 ÷ 1.33 = 9 studs, plus 3 plates (2 bottom plates + 1 top plate = 36 linear feet). Add 10–15% for waste and corners.

How much does lumber cost per board foot?

Dimensional lumber (2×4, 2×6) typically runs $0.80–$2.00 per board foot at big-box stores, depending on wood species and current prices. Cedar and pressure-treated lumber costs more.