International 1/4-Inch Log Rule (Clark Version) - Multi-Log Calculator
The International 1/4-Inch Log Rule (Clark Version) - Multi-Log Calculator lets you estimate the total board feet for multiple logs using Clark's polynomial formulas. It supports 4, 8, 12, 16, and 20-foot log lengths and provides an accurate approximation based on the small-end diameter measured inside the bark (DIB). This calculator includes a live result panel, running history, copy-to-clipboard, and CSV export features.
How to Use:
Click Add Log to enter multiple logs. Input the length and diameter of each log. Click Calculate to view board feet per log and total. Use Copy History or Download CSV to save your results.
Related Forestry Calculators:
International 1/4-Inch Log Rule (Clark Version) - Multi-Log Calculator
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Total Board Feet: 0
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Calculator
- Length (ft): choose the log length
- DIB (in): small-end diameter inside bark in inches (must be > 4")
Results
- Board Feet: Calculated per log using the International 1/4-Inch Log Rule
- History: Each entry is shown in a live text for copy or download
- Total Board Feet: Automatically summed and displayed
Clark's International 1/4-Inch Log Rule Formulas (per log length)
- 4 ft: \( BF = 0.199D^2 - 0.642D \)
- 8 ft: \( BF = 0.398D^2 - 1.086D - 0.271 \)
- 12 ft: \( BF = 0.597D^2 - 1.330D - 0.715 \)
- 16 ft: \( BF = 0.796D^2 - 1.375D - 1.230 \)
- 20 ft: \( BF = 0.995D^2 - 1.221D - 1.719 \)
Example 1 - 16 ft log, 14 in DIB
\[ \begin{align*} BF &= 0.796 \cdot 14^2 - 1.375 \cdot 14 - 1.230 \\ &= 0.796 \cdot 196 - 19.25 - 1.230 \\ &= 156.016 - 19.25 - 1.230 \\ &= 135.54 \end{align*} \]
Example 2 - 8 ft log, 10 in DIB
\[ \begin{align*} BF &= 0.398 \cdot 10^2 - 1.086 \cdot 10 - 0.271 \\ &= 0.398 \cdot 100 - 10.86 - 0.271 \\ &= 39.8 - 10.86 - 0.271 \\ &= 28.67 \end{align*} \]
Conversions:
one board foot (bf) = 0.0833333333333333 cubic feet (ft³) one board foot (bf) = 0.002359737216 cubic metres (m³)
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