Enter Board Dimensions
Quick Reference: Common Lumber Sizes
Based on nominal dimensions. Actual board feet use the actual milled size.
What Is a Board Foot?
A board foot is the standard unit for measuring lumber volume. One board foot equals a piece of wood 1 inch thick, 12 inches wide, and 12 inches long — or 144 cubic inches. Lumberyards and hardwood dealers price their stock by the board foot, so understanding this unit is essential for budgeting any woodworking or construction project.
The Board Feet Formula
The formula is simple: Board Feet = (Thickness x Width x Length) / 144, where thickness and width are in inches and length is in inches (or divide by 12 if length is in feet). Our calculator handles the math automatically — just enter your dimensions.
Nominal vs. Actual Dimensions
Lumber sold as "2x4" actually measures 1.5" x 3.5" after milling. When buying dimensional lumber (2x4, 2x6, etc.) from a big-box store, it's priced per linear foot — not board feet. Board foot pricing is most common for hardwoods and rough-sawn lumber from lumberyards. This calculator uses the actual dimensions you enter, so input the real measurements for accurate results.
When to Use Board Feet
- Buying rough-sawn hardwood from a lumberyard or sawmill
- Estimating material costs for furniture or cabinet projects
- Comparing prices between different lumber dealers
- Calculating how much raw lumber to order for a specific project
Always add 15-20% extra to your board feet total to account for waste, defects, and cutting loss. Hardwood lumber often has rough edges and knots that reduce usable yield.
For deck framing takeoffs, pair this with our joist span calculator so you can confirm the joist size first, then convert those framing members into lumber volume and cost.
After sizing beams and posts, use our deck footing calculator to check whether the support layout needs more footings or larger concrete piers before you finalize the lumber order.
Frequently Asked Questions
How do you calculate board feet?
Board feet = (Thickness in inches x Width in inches x Length in feet) / 12. For example, a board that is 1 inch thick, 6 inches wide, and 8 feet long is 4 board feet (1 x 6 x 8 / 12 = 4). Use actual measured dimensions, not nominal sizes.
What is the difference between board feet and linear feet?
Linear feet measures only length — a 10-foot board is 10 linear feet regardless of thickness or width. Board feet measures volume and accounts for all three dimensions. A 2-inch thick, 12-inch wide, 10-foot long board is 20 board feet but only 10 linear feet. Hardwood is sold by the board foot; dimensional lumber is often sold by the linear foot.
How much does a board foot of lumber cost?
Prices vary widely by species: common softwoods like pine cost $2-$5 per board foot, red oak runs $4-$8, hard maple is $5-$10, walnut costs $8-$15, and exotic species can exceed $20 per board foot. Prices also depend on grade, thickness, and whether the lumber is rough-sawn or surfaced.
Should I use nominal or actual dimensions for board feet?
Use actual dimensions for the most accurate calculation. A 2x4 is actually 1.5 x 3.5 inches, and a 1-inch board is actually 3/4 inch thick after milling. However, many lumberyards price rough-sawn hardwood using the nominal (pre-milling) thickness, so ask your supplier which convention they use.
How much extra lumber should I buy for waste?
Add 15-20% extra for most woodworking projects to account for cutting waste, defects, and mistakes. For hardwood with rough edges or knots, add 25-30%. It's better to have a little extra than to stop mid-project for another lumber run — especially if you need color-matched boards from the same batch.