Board Foot Calculator: How to Calculate Board Foot

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Photo: kasarp / Adobe Stock
Photo: kasarp / Adobe Stock
Highlights
  • Board feet is a volumetric unit of measurement used for wood. 

  • It’s not as common as square footage. 

  • Board foot measurements are mostly used for pricing and weight calculations.

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If you’re building a deck, bookshelf, wall, or birdhouse, you may need to understand how to calculate board feet. This unit of measurement is a precise calculation of the volume of the lumber you’ll need. Use the formula below to calculate board feet, but remember that not all projects require this unit of measurement. 

How Many Board Feet of Lumber Are Needed for Projects?

You can work backward from your lumber requirements to determine how many board feet you need for your project. Working with a pro helps, as certain projects are more difficult to measure compared to others. Use the table below as a rough guide to how many board feet are needed for individual projects.

ProjectBoard Foot Requirements
Birdhouse2 board ft.
Planter box10 board ft.
Small bookshelf15 board ft.
Garden bench25 board ft.
100 sq. ft. of wooden flooring100 board ft.
10-ft. x 10-ft. deck120 board ft.
8-ft. x 10-ft. shed 350 board ft.

How to Calculate Board Feet

The formula below shows you how to arrive at your final board foot requirements. Remember that a board foot can have multiple lengths, thicknesses, and widths, as long as when you plug in the numbers below, you arrive at 1 board foot.

Board Feet = Width (in inches) x Thickness (in inches) x Length (in feet) / 12

Using the formula above, assume a piece of wood has a length of 12 inches, a width of 6 inches, and a thickness of 2 inches. You would input the numbers as 6 x 2 x 1, and then divide by 12, resulting in an answer of 1 board foot. 

Board foot measurement example illustrated, calculating the cubic inches of a board

Who to Hire to Calculate Board Feet and Install Wood

If you’re undertaking a project where you need to know board foot requirements, talk to a local woodworking pro. They will help determine the amount of wood required for the project and which are the best types of wood to use. 

Frequently Asked Questions

A board foot is a volumetric unit and is primarily used for pricing and planning larger projects where volume is a factor. Pricing lumber by the board foot aids in understanding exactly how much wood you’re purchasing, as volume is a more accurate unit of measurement compared to square feet.

There are approximately 5.33 board feet in a 2x4. You can use the board foot calculator in this article to easily find the answer. A 2x4 is 2 inches of thickness by 4 inches of width, so you need to find the length, with 8 feet being the most common. You’d use the calculator here to multiply 2 times 4 times 8, and then divide by 12, arriving at a total of 5.33 board feet. 

The best lumber for building will be the strongest and most eco-friendly wood your budget allows. That being said, Douglas fir, pine, oak, and maple are all common building materials. Contractors will use a strong, inexpensive wood to frame a house or other structure and finer woods like mahogany for detail work. 

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