Use this Board Foot Calculator to quickly calculate the volume of lumber in board feet. It is useful for estimating lumber quantities and comparing wood prices for woodworking, construction, furniture projects, cabinetry, flooring, and other applications.
Enter the thickness, width, and length of a board to calculate the number of board feet.
Board Foot Calculator
The standard board foot formula is:
Board Feet = Thickness (in) × Width (in) × Length (ft) ÷ 12
For example, a board that is:
- 2 inches thick
- 8 inches wide
- 10 feet long
has:
2 × 8 × 10 ÷ 12 = 13.33 board feet
So the board contains approximately 13.33 board feet.
What Is a Board Foot?
A board foot is a unit of lumber volume commonly used in the United States and Canada.
One board foot represents a piece of wood measuring:
1 inch thick × 12 inches wide × 12 inches long
In other words:
1 board foot = 144 cubic inches of wood
Board feet measure volume, not the actual surface area or linear length of a board.
Because lumber is often sold by board foot, understanding this measurement can make it easier to estimate project costs.
Board Foot Formula
The most common formula is:
Board Feet = Thickness × Width × Length ÷ 12
Use:
- Thickness in inches
- Width in inches
- Length in feet
Example
For a board measuring 1.5 inches thick, 6 inches wide, and 8 feet long:
1.5 × 6 × 8 ÷ 12 = 6 board feet
The board contains 6 board feet.
How to Calculate Board Feet
Calculating board feet involves three basic measurements.
Step 1: Measure Thickness
Measure the board thickness in inches.
Step 2: Measure Width
Measure the board width in inches.
Step 3: Measure Length
Measure the board length in feet.
Step 4: Apply the Formula
Multiply thickness × width × length, then divide by 12.
Board Feet = T × W × L ÷ 12
If you have multiple boards, calculate each board and add the results together.
Board Foot Calculator Example
Suppose you need five boards, each measuring:
- 2 inches thick
- 6 inches wide
- 8 feet long
First calculate one board:
2 × 6 × 8 ÷ 12 = 8 board feet
Then multiply by five:
8 × 5 = 40 board feet
The total is 40 board feet.
Board Foot Calculator for Multiple Boards
For several boards with identical dimensions:
Total Board Feet = Board Feet per Board × Number of Boards
For example:
- Thickness: 1 inch
- Width: 8 inches
- Length: 10 feet
- Quantity: 12 boards
One board:
1 × 8 × 10 ÷ 12 = 6.67 board feet
For 12 boards:
6.67 × 12 = 80 board feet
The total volume is approximately 80 board feet.
Board Foot Calculator for Different-Sized Boards
If your project contains boards with different dimensions, calculate each group separately.
For example:
Group 1
10 boards:
1 × 6 × 8 ÷ 12 = 4 board feet each
Total:
10 × 4 = 40 board feet
Group 2
5 boards:
2 × 8 × 10 ÷ 12 = 13.33 board feet each
Total:
5 × 13.33 = 66.67 board feet
Project Total
40 + 66.67 = 106.67 board feet
The project requires approximately 106.67 board feet before accounting for waste.
Board Feet vs. Linear Feet
Board feet and linear feet are different measurements.
Linear feet measure length.
Board feet measure lumber volume and account for thickness and width as well as length.
For example, two boards can both be 10 linear feet long but contain very different numbers of board feet if their widths or thicknesses differ.
Board Feet vs. Square Feet
Square feet measure area.
Board feet measure volume.
A flooring project, for example, may be discussed in square feet, while rough lumber may commonly be priced by board foot.
The two measurements should not be treated as interchangeable.
Board Feet vs. Cubic Feet
Both board feet and cubic feet measure volume, but they use different units.
One board foot equals:
144 cubic inches
Since one cubic foot contains 1,728 cubic inches:
1 cubic foot = 12 board feet
Therefore:
Board Feet = Cubic Feet × 12
And:
Cubic Feet = Board Feet ÷ 12
Example
If a lumber order contains 50 board feet:
50 ÷ 12 = 4.17 cubic feet
The lumber contains approximately 4.17 cubic feet of wood volume.
Board Foot Calculator for Rough Lumber
Board feet are particularly useful when buying rough-sawn hardwood and other lumber sold according to volume.
The nominal dimensions may not always be the same as the actual dimensions after drying, surfacing, or milling.
When purchasing lumber, check whether the supplier calculates board feet using:
- Actual dimensions
- Nominal dimensions
- Rough dimensions
- Standard industry practices
Use the supplier’s measurement method when estimating the final cost.
Board Foot Calculator for Hardwood
Hardwood suppliers commonly list prices per board foot.
To estimate material cost:
Lumber Cost = Total Board Feet × Price per Board Foot
Example
If you need 80 board feet and the lumber costs $8 per board foot:
80 × $8 = $640
The estimated lumber cost is $640 before taxes, shipping, milling, waste, or other charges.
Actual prices vary by wood species, grade, thickness, width, availability, location, and supplier.
Board Foot Calculator for Woodworking
Board-foot calculations can be useful when planning:
- Tables
- Cabinets
- Shelves
- Benches
- Desks
- Furniture
- Cutting boards
- Doors
- Woodworking projects
However, the calculated volume is not necessarily the exact amount you should purchase.
Woodworking projects often require additional material because boards may contain:
- Knots
- Cracks
- Warp
- Splits
- Defects
- Grain irregularities
- Areas unsuitable for the finished project
How Much Extra Lumber Should I Buy?
The calculated board-foot requirement represents the theoretical volume.
Actual projects often require additional lumber because of cutting and defects.
A common planning approach is to add approximately 10% to 20% for waste, although the appropriate allowance depends heavily on the project.
Complex furniture projects, small parts, irregular designs, or highly selective wood grades may require more.
Example
If your calculated requirement is 100 board feet and you plan for 15% waste:
100 × 1.15 = 115 board feet
You would plan for approximately 115 board feet.
Nominal vs. Actual Lumber Dimensions
One important issue when calculating board feet is the difference between nominal and actual lumber dimensions.
A board described as a nominal 2 × 4 does not normally measure exactly 2 inches by 4 inches after standard processing.
If you are calculating board feet for purchased lumber, determine whether the calculation should use the nominal dimensions or actual dimensions.
For rough lumber, the supplier may use different conventions.
When purchasing expensive hardwood, ask the supplier how board footage is measured.
Board Foot Conversion
Board Feet to Cubic Feet
Because:
1 cubic foot = 12 board feet
the formula is:
Cubic Feet = Board Feet ÷ 12
Cubic Feet to Board Feet
Use:
Board Feet = Cubic Feet × 12
Board Feet to Cubic Inches
Since one board foot equals 144 cubic inches:
Cubic Inches = Board Feet × 144
Board Foot Calculation Table
Here are some common examples using the standard formula.
| Thickness | Width | Length | Board Feet |
|---|---|---|---|
| 1 in | 6 in | 8 ft | 4 |
| 1 in | 8 in | 10 ft | 6.67 |
| 2 in | 6 in | 8 ft | 8 |
| 2 in | 8 in | 10 ft | 13.33 |
| 2 in | 10 in | 12 ft | 20 |
| 3 in | 8 in | 10 ft | 20 |
| 4 in | 12 in | 10 ft | 40 |
These examples use the stated dimensions directly. Actual lumber purchasing calculations may differ when nominal dimensions or supplier-specific measurement conventions are used.
Board Foot Calculator for a Table
Suppose you’re building a table and need:
- 6 boards
- 2 inches thick
- 8 inches wide
- 8 feet long
One board:
2 × 8 × 8 ÷ 12 = 10.67 board feet
Six boards:
10.67 × 6 = 64 board feet
The theoretical requirement is approximately 64 board feet.
If you add 15% for waste:
64 × 1.15 = 73.6 board feet
You might therefore plan for approximately 74 board feet, subject to the actual lumber dimensions and project requirements.
Board Foot Calculator for Logs
Board feet can also be used to estimate the amount of lumber obtainable from logs, but log-volume calculations are more complicated.
Sawlog estimates may use log rules such as the Doyle, Scribner, or International rule.
These methods account for factors such as:
- Log diameter
- Log length
- Saw kerf
- Taper
- Slab waste
- Sawing method
A simple board-foot calculator should not be treated as a precise sawmill yield calculator.
For log-to-lumber estimates, use the appropriate log rule or sawmill calculation method.
Board Foot Calculator for Flooring
Board feet and square feet serve different purposes when estimating wood flooring.
If you know the required surface area and the thickness of the flooring, you can calculate the approximate lumber volume.
For example:
Board Feet = Thickness × Surface Area ÷ 12
when thickness is measured in inches and surface area is measured in square feet.
For a 1-inch-thick wood surface covering 200 square feet:
1 × 200 ÷ 12 = 16.67 board feet
This is a mathematical volume conversion and may not represent the actual amount of flooring material you need to purchase because flooring is typically purchased based on finished surface area plus an allowance for cuts and waste.
Common Board Foot Calculation Mistakes
Using Inches for Length
The standard formula above expects length in feet.
If length is measured in inches, convert it to feet first.
Forgetting to Divide by 12
Thickness and width are measured in inches while length is measured in feet. The division by 12 is necessary for the standard formula.
Confusing Board Feet With Linear Feet
Linear feet only measure length. Board feet account for thickness, width, and length.
Ignoring Lumber Dimensions
Nominal and actual lumber dimensions can differ. Confirm which dimensions your supplier uses.
Forgetting Waste
The theoretical board-foot total does not automatically account for defects, cutting, milling, or unusable sections.
Assuming Board-Foot Pricing Includes Everything
A lumber price per board foot may not include milling, surfacing, shipping, taxes, or other charges.
Frequently Asked Questions
What is a board foot?
A board foot is a unit of lumber volume equal to a piece of wood measuring 1 inch thick, 12 inches wide, and 12 inches long.
What is the board foot formula?
The standard formula is:
Board Feet = Thickness (inches) × Width (inches) × Length (feet) ÷ 12
How many cubic feet are in a board foot?
One board foot equals 1/12 of a cubic foot.
How many board feet are in one cubic foot?
One cubic foot contains 12 board feet.
How do I calculate board feet for multiple boards?
Calculate the board footage of one board and multiply by the number of boards if all boards have identical dimensions.
How do I calculate board feet for different boards?
Calculate each board or each group of boards separately, then add all the board-foot values together.
Is board foot the same as square foot?
No. A square foot measures area, while a board foot measures lumber volume.
Is board foot the same as linear foot?
No. Linear feet measure length only. Board feet account for thickness, width, and length.
How much waste should I allow when buying lumber?
A general planning allowance may be around 10% to 20%, but the appropriate amount depends on the project, lumber quality, design, and cutting requirements.
Can I use actual lumber dimensions?
Yes. If you know the actual dimensions and your supplier uses actual measurements, use those dimensions in the formula.
Why does lumber pricing use board feet?
Board feet provide a way to price lumber according to volume while accounting for differences in thickness and width.
Can I calculate the cost of lumber with board feet?
Yes. Multiply the total board feet by the supplier’s price per board foot:
Total Cost = Board Feet × Price per Board Foot
Does a 2 × 4 contain 2 × 4 board feet?
No. The board-foot calculation depends on the board’s actual or specified dimensions and length. A board described as 2 × 4 does not automatically contain 8 board feet.
Final Thoughts
The Board Foot Calculator provides a convenient way to estimate lumber volume and understand board-foot pricing.
The key formula is:
Board Feet = Thickness × Width × Length ÷ 12
Use thickness and width in inches and length in feet.
For larger woodworking and construction projects, remember that the calculated result represents theoretical lumber volume. Actual purchasing requirements can be higher because of defects, cutting waste, milling, dimensional changes, and supplier-specific measurement practices.
When ordering lumber, confirm the supplier’s board-foot calculation method and allow enough material for your project’s expected waste.