🪵 Lumber Dimensions Guide

Softwood dimensional lumber specifications

Understanding Lumber Sizes

Dimensional lumber sold at hardware stores uses a "nominal" naming convention that originated when lumber was sold in its rough-sawn state. Modern lumber is kiln-dried and surfaced on all four sides (S4S), resulting in smaller actual dimensions.

Size Reduction Rules

  • Boards under 2" nominal: Lose approximately 1/4" to 1/2"
  • 2" nominal thickness: Actual is 1.5" (loses 1/2")
  • Widths 2-6" nominal: Lose 1/2"
  • Widths 8"+ nominal: Lose 3/4"

Data Sources

All lumber dimensions and specifications are sourced from:
• ASTM D245: Standard Practice for Establishing Wood Properties for Structural Design
• NLGA Standards: National Lumber Grades Authority grading and sizing rules
• USDA Forest Service: Wood Handbook - Wood as an Engineering Material
• Pressure-Treated Specifications: American Wood Preservers' Association (AWPA) standards

Weight by Species

Lumber weight varies significantly by wood species. Pressure-treated wood is the heaviest due to the chemical treatment process that saturates the wood with preservatives.

SpeciesDensity (lb/ft³)Use Case
Douglas Fir/Pine~32Standard framing
Western Red Cedar~22Fencing, siding (rot resistant)
Pressure Treated~50Ground contact, decks

Complete Lumber Reference

NominalActualWeight/ft (Pine)Weight/ft (Treated)
1x23/4" x 1-1/2"0.20 lbs0.36 lbs
1x33/4" x 2-1/2"0.33 lbs0.59 lbs
1x43/4" x 3-1/2"0.46 lbs0.82 lbs
1x63/4" x 5-1/2"0.72 lbs1.29 lbs
1x83/4" x 7-1/4"0.95 lbs1.70 lbs
1x103/4" x 9-1/4"1.21 lbs2.17 lbs
1x123/4" x 11-1/4"1.47 lbs2.64 lbs
2x21-1/2" x 1-1/2"0.50 lbs0.78 lbs
2x31-1/2" x 2-1/2"0.83 lbs1.30 lbs
2x41-1/2" x 3-1/2"1.28 lbs2.00 lbs
2x61-1/2" x 5-1/2"2.05 lbs3.21 lbs
2x81-1/2" x 7-1/4"2.70 lbs4.22 lbs
2x101-1/2" x 9-1/4"3.44 lbs5.38 lbs
2x121-1/2" x 11-1/4"4.18 lbs6.53 lbs
4x43-1/2" x 3-1/2"3.80 lbs5.94 lbs
4x63-1/2" x 5-1/2"5.97 lbs9.33 lbs
6x65-1/2" x 5-1/2"9.38 lbs14.66 lbs

Pro Tip: When calculating weight for your vehicle, always use the pressure-treated values if there's any chance the lumber has been treated. The extra weight can make a significant difference for safety.

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