The Basic Formula
A board foot (BF) is the standard unit of measurement for lumber volume. One board foot equals a piece of wood 1 inch thick, 12 inches wide, and 12 inches long — or 144 cubic inches. The formula: Board Feet = (Thickness in inches x Width in inches x Length in feet) / 12.
For example: a 2x6 board that is 10 feet long contains (2 x 6 x 10) / 12 = 10 board feet. A 4x4 post that is 8 feet long contains (4 x 4 x 8) / 12 = 10.67 board feet.
Important Notes for Reclaimed Lumber
Board foot calculations for reclaimed lumber should use actual dimensions, not nominal dimensions, since reclaimed stock often measures at or near full nominal size. A reclaimed 2x4 that actually measures 2 inches by 4 inches contains (2 x 4 x L) / 12 board feet — about 15% more wood than a modern 2x4 at 1.5 x 3.5 inches.
When ordering reclaimed lumber from GreenBoard, specify whether your quantity is based on nominal or actual dimensions so we can pull the correct amount. We default to nominal board foot calculations unless otherwise specified.
Quick Reference
Board feet per linear foot for common sizes: 1x4 = 0.33 BF/LF, 1x6 = 0.50, 1x8 = 0.67, 1x12 = 1.00, 2x4 = 0.67, 2x6 = 1.00, 2x8 = 1.33, 2x10 = 1.67, 2x12 = 2.00, 4x4 = 1.33, 6x6 = 3.00, 8x8 = 5.33.
To estimate a project: multiply the coverage area (sq ft) by the board thickness in inches, then add 10-15% for waste and cutting. For example, a 200 sq ft accent wall using 1-inch-thick boards needs roughly 200 x 1 = 200 BF, plus 10% waste = 220 BF.