For woodworkers, cabinet makers, and lumber suppliers, the "board foot" is the standard unit of measurement for hardwood lumber. Unlike simple length or area, a board foot is a measure of volume, providing a consistent way to price and quantify lumber regardless of the board's specific dimensions. Our Board Foot Calculator is a straightforward tool designed to help you quickly calculate the volume of your lumber in board feet, making it easy to plan projects, estimate costs, and purchase the right amount of material.
How to Use the Board Foot Calculator
Calculating the board feet for a piece of lumber is simple:
- Enter Length: Input the length of your board in feet.
- Enter Width: Input the nominal width of your board in inches.
- Enter Thickness: Input the nominal thickness of your board in inches.
- Calculate Board Feet: Click the "Calculate" button to see the total volume of your lumber in board feet.
What is a Board Foot?
A board foot is a unit of volume equal to a piece of wood that is 12 inches long, 12 inches wide, and 1 inch thick. This is equivalent to 144 cubic inches of wood.
The Board Foot Formula
The standard formula for calculating board feet is:
Board Feet = [Length (ft) × Width (in) × Thickness (in)] / 12
For example, let's calculate the board feet for a common piece of hardwood lumber that is 8 feet long, 6 inches wide, and 1.5 inches thick:
(8 ft × 6 in × 1.5 in) / 12 = 72 / 12 = 6 board feet.
This formula is the industry standard used by lumberyards to price hardwood. By calculating the total board feet you need for a project, you can accurately estimate your material costs.
Nominal vs. Actual Dimensions: The "Quarter" System
One of the most important concepts to understand when buying hardwood is the difference between "nominal" and "actual" thickness. Hardwood lumber is typically sold in a "quarter" system based on its rough-sawn, nominal thickness.
- 4/4 ("Four-Quarter") Lumber: Has a nominal thickness of 1 inch. After milling and surfacing, its actual thickness is usually closer to 13/16 inch to 7/8 inch.
- 5/4 ("Five-Quarter") Lumber: Has a nominal thickness of 1.25 inches. Its actual finished thickness is often around 1 1/8 inches.
- 8/4 ("Eight-Quarter") Lumber: Has a nominal thickness of 2 inches. Its actual finished thickness is often around 1 3/4 inches.
Crucially, board footage and pricing are almost always based on the nominal thickness, not the final, actual thickness of the surfaced board you buy. When you use our calculator, you should input the nominal thickness (e.g., 1 for 4/4, 1.25 for 5/4) to get a cost estimate that aligns with how lumber is sold.
Planning Your Woodworking Project
Calculating Total Board Feet Needed
To plan a project, you should create a "cut list"—a list of every individual piece of wood you will need, along with its final dimensions. Calculate the board feet for each piece on your list and add them all together to get a total.
Don't Forget the Waste Factor
Just like with flooring or paint, you must always account for waste. You will lose material to saw kerfs (the width of the saw blade), mistakes, and cutting around defects in the wood like knots or cracks. It is standard practice to add a 15-25% waste factor to your total calculated board footage to ensure you have enough material to complete your project without running out. For wood with many defects or for complex projects with many angled cuts, you may want to use an even higher wastage factor.
Frequently Asked Questions
Why is lumber sold by board feet instead of by the board?
Hardwood lumber comes in random widths and lengths. Selling it by volume (board feet) creates a standardized pricing system that is fair for both the buyer and the seller, regardless of the specific dimensions of any single board.
How is this different from a linear foot?
A linear foot is simply a measure of length (12 inches). It does not account for the width or thickness of the wood. Linear feet are often used for pricing trim, molding, or construction lumber (like 2x4s), where the width and thickness are standard. Board feet are used for hardwood, where dimensions are variable.
What does S2S or S4S mean?
These terms describe how the lumber has been milled. S2S means "surfaced two sides," indicating the two faces of the board have been planed flat, but the edges are still rough. S4S means "surfaced four sides," indicating the board has been planed and jointed on all four sides to be perfectly flat and square.