Board Foot Calculator

Calculate board feet from lumber thickness, width, length, and quantity. Get instant volume estimates in Imperial or Metric units, with a clear breakdown for each board and the full quantity.

What Is a Board Foot?

A board foot (BF) is a unit used to measure lumber volume. One board foot equals a piece of wood 12 inches wide, 12 inches long, and 1 inch thick — a total of 144 cubic inches.

Board feet are commonly used to estimate quantities and compare lumber volumes. Unlike linear feet, board feet account for the thickness and width of a board as well as its length.

How to Calculate Board Feet

Enter the thickness, width, length, and number of pieces. The calculator updates the result automatically as you change the measurements.

For Imperial measurements, enter thickness and width in inches and length in feet. For Metric measurements, enter thickness and width in millimeters and length in meters.

The calculation uses the dimensions you enter. It does not automatically convert nominal lumber sizes into actual dressed dimensions.

Board Foot Formula

For Imperial measurements:

Board Feet = (Thickness × Width × Length × Quantity) / 12

Where:

• Thickness is measured in inches.
• Width is measured in inches.
• Length is measured in feet.
• Quantity is the number of identical pieces.

For Metric measurements:

Board Feet = (Thickness × Width × Length × Quantity) / 2359.737216

Where thickness and width are in millimeters and length is in meters.

Both formulas calculate the same geometric volume when equivalent dimensions are supplied.

Board Foot Calculation Example

Suppose you have ten boards with these dimensions:

Reference table: Measurement, Value

Measurement	Value
Thickness	2 in
Width	6 in
Length	8 ft
Quantity	10

Board Feet = (2 × 6 × 8 × 10) / 12 = 80 BF

The total is 80 board feet, or 8 board feet per piece.

This example uses nominal dimensions. If the boards have been surfaced and you need their actual physical volume, enter their actual measured dimensions instead.

Nominal vs Actual Lumber Dimensions

In North America, lumber is often sold using nominal dimensions. A nominal 2×4, for example, commonly measures 1½ × 3½ inches after drying and surfacing.

This distinction matters when calculating board feet.

For a nominal 2×4 that is 8 feet long:

• Using nominal dimensions: approximately 5.33 BF.
• Using dressed dimensions of 1½ × 3½ inches: 3.50 BF of actual geometric volume.

Both calculations are mathematically valid, but they describe different measurement bases.

Use the dimensions appropriate to your task. Commercial lumber tally may follow nominal measurement conventions, while physical volume estimates should use actual dimensions.

For common lumber dimensions, see the Lumber Sizes Chart.

Common Board Foot Calculation Mistakes

Mixing feet and inches. The Imperial formula expects thickness and width in inches, but length in feet.

Confusing nominal and actual sizes. The same board can produce different volume figures depending on which dimensions are used.

Forgetting the quantity. Multiply the volume of one piece by the number of identical boards.

Confusing board feet with linear feet. Linear feet measure length only. Board feet include all three dimensions.

Frequently Asked Questions

How many cubic inches are in one board foot?

One board foot equals exactly 144 cubic inches, or 1/12 of a cubic foot.

How many board feet are in a 2×4×8?

Using nominal dimensions of 2 × 4 inches and a length of 8 feet, the result is approximately 5.33 board feet. Using common dressed dimensions of 1½ × 3½ inches, the geometric volume is 3.50 board feet.

Should I use nominal or actual dimensions?

Use the measurement basis that matches your purpose. Nominal dimensions may be appropriate for lumber purchasing and tally conventions. Actual dimensions are appropriate when calculating physical volume.

Can I calculate board feet using Metric units?

Yes. Switch to Metric and enter thickness and width in millimeters and length in meters. The calculator converts the measurements into board feet.

Does the calculator include cutting waste?

No. The result is based on the dimensions and quantity entered. Any extra material needed for cutting, defects, or project waste must be estimated separately.

Related Reference

Nominal vs Actual Lumber Sizes

Compare common US lumber dimensions and understand how surfaced sizes differ from nominal measurements.

View Lumber Sizes Chart

Technical Sources

• NIST — American Softwood Lumber Standard PS 20-25 (replaces the obsolete PS 20-20 reference; nominal/dressed measurement basis and Table 3).
• University of Missouri Extension — How to Measure Trees and Logs (definition: 1 board foot equals 144 cubic inches; use only the relevant definition, not log scaling as calculator logic).