How Do You Figure Board Feet In A Log

How Do You Figure Board Feet in a Log?

If you’ve ever bought or sold lumber, you might have heard the term “board feet.” But how exactly do you calculate it from a log? Board feet are a standard unit of measurement in the lumber industry, representing the volume of wood. Understanding how to figure board feet in a log is essential for accurate pricing, resource management, and ensuring you get fair value for your wood. This article will walk you through the process, explain the formulas used, and highlight factors that influence the calculation.

What Is a Board Foot?

A board foot is a unit of volume used to measure lumber. It is defined as a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long. This equals 144 cubic inches of wood. While it might seem like a simple concept, calculating board feet from a log involves more than just measuring dimensions. Logs are irregular in shape, and the way they are sawn into boards affects the total yield.

The key to figuring board feet lies in understanding that not all wood in a log is usable. Factors like knots, cracks, and the log’s taper (the gradual change in diameter from one end to the other) reduce the amount of usable wood. This is where specific formulas come into play.

The Basic Formula for Board Feet

The most straightforward way to calculate board feet is by using the basic formula:

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

This formula works well for individual boards, but logs require a different approach. Since logs are not straight or uniform, the calculation must account for their irregularities. However, this formula is still useful when you’re cutting a log into specific boards. For example, if you have a log that is 2 inches thick, 8 inches wide, and 10 feet long, the calculation would be:

(2 × 8 × 10) ÷ 12 = 160 ÷ 12 ≈ 13.33 board feet.

This gives you an estimate of the usable wood from that specific board. However, when dealing with an entire log, you need to consider how it is sawn and the formulas designed for log volume.

Log-Specific Calculations: Scribner and Doyle Formulas

When calculating board feet in a log, two primary formulas are used: the Scribner formula and the Doyle formula. These formulas are designed to estimate the volume of usable lumber in a log, taking into account its diameter and length.

1. The Scribner Formula

The Scribner formula is widely used in the United States and is considered more conservative. It is calculated as:

**Board Feet = [(Diam