Lumber Calculator
Lumber is sold by the board foot — a unit that accounts for thickness, width, and length. This calculator tells you exactly how many board feet each piece contains and the total board footage for your entire order, helping you price and purchase the right amount of lumber.
Advertisement
Calculator
See your Lumber Calculator results
Enter your email to unlock results — free forever.
No spam, ever. Unsubscribe at any time.
Advertisement
Formula
BF = (Thickness × Width × Length) / 12
Thickness and Width are in inches, Length is in feet. Dividing by 12 converts the result to board feet. Multiply by quantity to get the total board footage for your order.
How to use the Lumber Calculator
- 1
Enter your thickness (in)
Value should be in in.
- 2
Enter your width (in)
Value should be in in.
- 3
Enter your length (ft)
Value should be in ft.
- 4
Enter your quantity (boards)
- 5
Read your results instantly
Results update in real time as you type.
Advertisement
What Is a Board Foot?
A board foot is a volume measurement equal to a piece of lumber 12 inches long, 12 inches wide, and 1 inch thick — essentially 144 cubic inches. It's the standard unit for buying hardwood lumber at mills and specialty suppliers. Dimensional softwood (like 2×4s at the hardware store) is usually sold by the lineal foot, but board feet are used for pricing larger quantities and custom cuts.
Nominal vs. Actual Lumber Dimensions
A 2×4 is not actually 2 inches by 4 inches — after drying and planing, it measures 1.5" × 3.5". Use actual dimensions, not nominal, when calculating board feet for precise material costs. For rough-sawn hardwood lumber, use the full nominal dimension as the wood has not been surfaced. Your supplier can clarify whether you're buying rough or S4S (surfaced on 4 sides) lumber.
Tips & Insights
Use Actual Dimensions
For finished dimensional lumber, use actual measurements (e.g. 1.5" × 3.5" for a 2×4) to get accurate board footage and cost estimates.
Add 15% for Cuts and Waste
For framing projects, add 10–15% to your board foot total to account for cuts, defects, and mistakes. Complex cuts or short pieces increase waste.
Check Moisture Content
Kiln-dried lumber (KD) is more dimensionally stable than green lumber. For interior projects, use KD lumber to prevent warping and shrinkage after installation.
Worked Examples
Deck Framing Order
320 total board feet — plan to add 15% waste for a final order of around 368 BF.
Bookshelf Build
40 total board feet of 1×10 common board for a basic 6-shelf bookcase.
Advertisement
Frequently Asked Questions
How do you calculate board feet?
Board feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12. A 2×4×8 contains (2 × 4 × 8) / 12 = 5.33 board feet.
What is the difference between board feet and linear feet?
Linear feet measure only length, regardless of width or thickness. Board feet measure volume (a 3D unit). Hardware stores sell dimensional lumber by the linear foot; lumber yards sell hardwood by the board foot.
How many board feet are in a 2×4×8?
A 2×4×8 contains (2 × 4 × 8) / 12 = 5.33 board feet using nominal dimensions.
Why is a 2×4 not 2 inches by 4 inches?
Lumber is named by its rough-sawn dimensions before drying and surfacing. After the milling process, a 2×4 measures approximately 1.5" × 3.5". This industry standard dates back many decades.
How much does a board foot of lumber cost?
Common softwood lumber runs $1–$3 per board foot. Hardwoods like oak or maple range from $5–$15+ per board foot. Exotic species can be $20–$50+ per board foot.
Advertisement