Sawmill Log-to-Board-Feet Calculator

How this calculator works

Each rule estimates board feet from small-end diameter (D, inside bark) and log length (L):

• Doyle: (D−4)² × L / 16
• Scribner (Bruce & Schumacher formula): (0.79D² − 2D − 4) × L / 16
• International ¼-inch: 0.905 × (0.22D² − 0.71D), applied per 4-foot section

Doyle assumes a large slab/edging allowance that overpenalizes small logs; Scribner is diagram-based and doesn't account for log taper; International ¼" adds a small taper allowance and is generally regarded as the closest match to actual sawn lumber yield, especially for smaller logs.

A note on accuracy

The full official International ¼" rule adjusts diameter slightly for taper on logs longer than 4 feet; this calculator applies the base formula scaled by length without that taper correction, which is accurate to within a few percent for typical log lengths but won't exactly match official International scale tables for very long logs.

Where these formulas come from

• Doyle and Scribner (Bruce & Schumacher correction) formulas: Purdue University Extension, FNR-191
• International ¼-inch rule formula: Cornell University Cooperative Extension Forest Connect program

All three rules assume diameter is measured inside the bark at the small end of the log. Actual mill yield also depends on saw kerf, operator skill, and how the log is bucked — treat this as an estimate for planning, not a guaranteed yield.