Board Foot Calculator
1 board foot = 144 in³ = 1/12 ft³. Formula: BF = (L × W × T) / 144 (all dimensions in inches).
- Board foot definition: 1 BF = 144 in³ = 1/12 ft³.
- Formula: BF = (Length × Width × Thickness) / 144 when all dimensions are in inches.
- Mixed ft/in and m/cm inputs are converted to inches first, then used in the standard formula.
Important Note: Board feet measure lumber volume, not surface area or linear length. One board foot equals a board that is 12 inches long, 12 inches wide, and 1 inch thick, or 144 cubic inches. Results depend on whether you enter actual lumber dimensions or nominal lumber dimensions, so always check how your supplier prices the wood.
Use this Board Foot Calculator to estimate lumber volume and optional material cost from thickness, width, length, number of pieces, and price per board foot. It is useful for woodworking, hardwood buying, sawmill planning, cabinet projects, furniture making, and rough lumber estimates.
Reviewed by: AjaxCalculators Editorial Team
Last updated: May 2026
Method source: Standard board foot volume formula
Editorial standards: AjaxCalculators Editorial Policy
What This Board Foot Calculator Calculates
This calculator estimates:
- Board feet per piece
- Total board feet for multiple identical pieces
- Total cost when price per board foot is entered
- Step-by-step formula substitution
- Unit-converted dimensions when non-inch units are selected
The calculator supports common length, width, and thickness units such as millimeters, centimeters, meters, inches, feet, ft/in, and m/cm. It converts the dimensions to inches before applying the standard board foot formula.
Board Foot Formula
A board foot is a volume measurement used for lumber. The standard formula is:
Board feet = Length × Width × Thickness ÷ 144
Where all three dimensions are measured in inches.
| Variable | Meaning | Required Unit in Formula |
|---|---|---|
| Length | Length of the board | Inches |
| Width | Width of the board | Inches |
| Thickness | Thickness of the board | Inches |
| 144 | Cubic inches in one board foot | 12 × 12 × 1 |
If the length is entered in feet and the width and thickness are entered in inches, the formula can also be written as:
Board feet = Length in feet × Width in inches × Thickness in inches ÷ 12
How the Board Foot Calculator Works
The calculator follows these steps:
- Converts thickness, width, and length into inches.
- Multiplies length × width × thickness to find cubic inches per piece.
- Divides cubic inches by 144 to find board feet per piece.
- Multiplies board feet per piece by the number of pieces.
- If a price per board foot is entered, multiplies total board feet by the price.
| Result | Formula |
|---|---|
| Board feet per piece | (Length × Width × Thickness) ÷ 144 |
| Total board feet | Board feet per piece × number of pieces |
| Total cost | Total board feet × price per board foot |
Worked Example
Suppose you want to calculate the board footage for 6 boards. Each board is:
- Thickness: 2 inches
- Width: 8 inches
- Length: 10 feet
- Number of pieces: 6
- Price: $7.50 per board foot
First, convert length to inches:
10 feet × 12 = 120 inches
Now calculate board feet per piece:
Board feet = 120 × 8 × 2 ÷ 144
Board feet = 1,920 ÷ 144 = 13.33 board feet per piece
Now multiply by 6 pieces:
Total board feet = 13.33 × 6 = 80 board feet
Now calculate cost:
Total cost = 80 × $7.50 = $600
So, the project needs approximately 80 board feet of lumber, with an estimated cost of $600.
Board Feet vs Linear Feet vs Square Feet
Board feet, linear feet, and square feet are not the same measurement. Choosing the wrong unit can cause major lumber-ordering mistakes.
| Measurement | What It Measures | Example Use |
|---|---|---|
| Board feet | Lumber volume | Hardwood boards, rough lumber, sawmill pricing |
| Linear feet | Length only | Trim, moulding, boards sold by length |
| Square feet | Surface area | Flooring, plywood coverage, wall area |
A board can have the same linear footage as another board but a very different board-foot volume if the width or thickness is different.
Nominal vs Actual Lumber Dimensions
Board foot calculations can be affected by whether you use nominal or actual lumber dimensions.
| Dimension Type | Meaning | Why It Matters |
|---|---|---|
| Nominal dimensions | The common trade size, such as 2 × 4 | May not match the board’s actual measured size |
| Actual dimensions | The real measured thickness, width, and length | Gives a more direct physical volume estimate |
| Rough lumber dimensions | Dimensions before surfacing or planing | Often used in hardwood and sawmill contexts |
For accurate purchasing, check whether the lumber seller prices board feet using rough, nominal, or actual dimensions.
Common Board Foot Examples
| Board Size | Length | Approximate Board Feet |
|---|---|---|
| 1 in × 6 in | 8 ft | 4 board feet |
| 1 in × 12 in | 8 ft | 8 board feet |
| 2 in × 4 in | 8 ft | 5.33 board feet |
| 2 in × 6 in | 10 ft | 10 board feet |
| 2 in × 8 in | 10 ft | 13.33 board feet |
| 4 in × 4 in | 8 ft | 10.67 board feet |
How to Use This Board Foot Calculator
- Enter the number of identical pieces.
- Optionally enter the price per board foot if you want a cost estimate.
- Enter the board thickness and select the correct unit.
- Enter the board width and select the correct unit.
- Enter the board length and select the correct unit.
- Click Calculate to estimate board feet per piece, total board feet, and total cost.
- Use Reset to clear the fields and start again.
- Use Download PDF if you want to save or print the calculation.
How to Interpret the Results
| Result | Meaning | Important Caution |
|---|---|---|
| Board feet per piece | The lumber volume of one board or piece. | Only valid for the dimensions entered. |
| Total board feet | Total lumber volume for all pieces. | Add waste allowance for cutting, defects, trimming, and mistakes. |
| Total cost | Estimated material cost based on price per board foot. | Actual prices may vary by species, grade, moisture, surfacing, supplier, and location. |
When to Add a Waste Allowance
The calculated board footage is the mathematical volume of the pieces entered. Real projects often need more lumber than the exact calculated amount.
| Project Type | Possible Waste Allowance | Reason |
|---|---|---|
| Simple straight cuts | 5% to 10% | Trimming, saw kerf, minor mistakes |
| Furniture or cabinetry | 10% to 20% | Grain selection, joinery, defects, matching parts |
| Rough lumber | 15% to 30% or more | Warp, checks, knots, milling, drying, and surfacing loss |
The right waste allowance depends on wood species, board quality, project layout, cutting plan, and how much matching or defect removal is needed.
Practical Uses
- Estimating hardwood lumber purchases
- Planning woodworking and furniture projects
- Comparing lumber prices from different suppliers
- Checking sawmill or rough lumber quantities
- Estimating project cost from board-foot pricing
- Converting mixed units into standard board-foot volume
Common Mistakes
- Using feet for every dimension without converting to inches first.
- Confusing board feet with square feet.
- Confusing board feet with linear feet.
- Entering nominal dimensions when the seller uses actual dimensions, or the other way around.
- Forgetting to multiply by the number of pieces.
- Forgetting waste allowance for cutting, milling, defects, or mistakes.
- Assuming the lowest price per board foot always gives the lowest usable project cost.
Assumptions and Limitations
- The calculator assumes rectangular boards or pieces.
- It assumes the dimensions entered represent the lumber dimensions you want to calculate.
- It converts all dimensions to inches before applying the board-foot formula.
- It does not account for saw kerf, trimming, milling loss, defects, knots, checking, cupping, bowing, twist, or waste.
- It does not evaluate wood grade, moisture content, species, strength, appearance, or suitability for a project.
- It does not determine whether a board is priced by nominal, actual, rough, or surfaced dimensions.
- Total cost is an estimate only and depends on the price entered by the user.
References
- Ohio State University Extension — Measuring Standing Trees and Board Foot Definition
- University of Tennessee Extension — Estimating Weight of Logs and Standing Timber
- NIST — SI Units and Unit References
Related Calculators
- Square Footage Calculator
- Decking Calculator
- Flooring Calculator
- Wood Weight Calculator
- Cubic Feet Calculator
Frequently Asked Questions
What is a board foot?
A board foot is a lumber volume measurement. One board foot equals 144 cubic inches, which is the volume of a board 12 inches long, 12 inches wide, and 1 inch thick.
How do I calculate board feet?
Multiply length, width, and thickness in inches, then divide by 144. If length is in feet while width and thickness are in inches, multiply length in feet by width in inches by thickness in inches, then divide by 12.
Is board foot the same as square foot?
No. A square foot measures area, while a board foot measures lumber volume. Board feet include thickness, but square feet do not.
Is board foot the same as linear foot?
No. A linear foot measures length only. Board feet include length, width, and thickness.
Should I use nominal or actual dimensions?
Use the dimensions that match how the lumber is being priced or measured. Hardwood and rough lumber may be sold using rough or actual dimensions, while some retail lumber is commonly described with nominal dimensions.
Does this calculator include waste?
No. The calculator gives the mathematical board footage for the dimensions entered. Add extra lumber for cutting waste, defects, milling loss, grain selection, and mistakes.
Why is price per board foot optional?
Price is optional because the calculator can estimate lumber volume without cost. If you enter a price per board foot, it also estimates total material cost.
Can I use this for logs or standing trees?
This calculator is best for rectangular boards or lumber pieces. Logs and standing trees require log rules, taper assumptions, sawmill yield estimates, and waste factors, so they should not be calculated the same way as rectangular boards.
Disclaimer
This Board Foot Calculator provides general lumber-volume and cost estimates only. It does not account for waste, saw kerf, milling loss, defects, moisture content, grade, species, surfacing, nominal-versus-actual pricing rules, or supplier-specific measurement practices. Always confirm measurements, pricing method, waste allowance, and material requirements with your lumber supplier, sawmill, contractor, or project plan before purchasing materials.