What Board Feet Means in Lumber Buying
If you’ve ever priced hardwood at a lumber yard, you’ve probably seen “BF”, “bd ft”, or “board foot” on the tag. Board feet is a volume measurement that lets lumber sellers price boards fairly even when the pieces vary in width, thickness, and length. Instead of selling every board as a “piece,” board feet turns the board into a standardized volume number you can total across a project.
This is especially helpful for woodworking, cabinetry, furniture building, and finish carpentry where boards aren’t always the same width. It’s also common for rough-sawn stock where the exact surfaced thickness may differ from board to board. With a board foot calculator, you can estimate how much wood you’re really buying, plan your cut list, and forecast cost before you step into the shop.
Board Foot Definition
One board foot is the volume of a board that measures: 1 inch thick × 12 inches wide × 12 inches long. That equals 144 cubic inches. Since it’s a volume unit, any board that has the same volume counts as one board foot, even if it’s shaped differently.
= 1 in × 12 in × 12 in
= 144 in³
Board Foot Formula for Lumber
The standard board foot formula depends on how you measure length. Most woodworkers measure thickness and width in inches, while length is usually measured in feet. That creates the simplest and most common version:
BF = (Thickness(in) × Width(in) × Length(ft)) ÷ 12
If your length is measured in inches instead of feet, the denominator changes because you’re staying in inches for all three dimensions:
BF = (Thickness(in) × Width(in) × Length(in)) ÷ 144
Why the ÷ 12 Works
When length is in feet, you’re mixing inches and feet. A board foot is based on a 12-inch length (one foot). So dividing by 12 converts that “feet” length scale into the 12-inch reference built into the board foot definition. That’s why the formula is so widely used in shops and yards: it’s quick, consistent, and easy to multiply across quantities.
How to Calculate Board Feet for Sheet Goods
Sheet goods like plywood, MDF, and some engineered panels are often priced per sheet, but board feet can still be useful for comparisons and estimating volume. Sheet goods are essentially “thickness × area.” Since 1 board foot equals 1 inch of thickness over 1 square foot of area, the formula becomes:
BF = Thickness(in) × Area(ft²)
Example: a 3/4" sheet that is 4×8 feet has an area of 32 ft². Multiply by thickness in inches: 0.75 × 32 = 24 board feet. This tool includes a dedicated sheet tab so you don’t have to manually compute area.
Nominal vs Actual Lumber Size
One of the biggest sources of confusion is the difference between nominal and actual sizes. A “2×4” is a name, not its true measurement. After drying and planing, common 2×4 lumber typically measures about 1.5 × 3.5 inches. If you calculate board feet with nominal dimensions, you’ll usually overestimate volume and cost.
That’s why this calculator includes a “Nominal Lumber” mode that uses common actual sizes for quick estimates. For maximum accuracy—especially in furniture work—measure the board or use the surfaced size you’re buying (S2S, S3S, S4S).
Waste Factor: Planning for Real Cuts
Real woodworking is not perfectly efficient. Offcuts, knots, checks, warping, and grain matching all reduce usable yield. A waste factor helps you plan for that reality. In many projects, a waste allowance of 5–15% is typical, but it can be higher for complex layouts, tight grain matching (table tops), or highly selective cutting.
This tool lets you add a waste percentage to your total board feet. You’ll see: the “raw” board feet (your dimensions), plus “board feet with waste” to help you buy enough material without running short.
Cost Estimation with Price per Board Foot
Lumber pricing often uses a price per board foot, especially for hardwoods. Once you know total board feet, cost is straightforward: total BF × price per BF. If you apply waste, you can price the “with waste” total for a safer estimate.
Keep in mind: actual invoices may include grading, milling, surfacing fees, minimum quantities, or rounding to the nearest increment. Use the estimate to budget and compare options, then confirm details with your supplier.
Common Use Cases for a Board Foot Calculator
- Furniture builds: estimate hardwood for tables, cabinets, shelving, and frames.
- Shop planning: convert a cut list into total material required.
- Comparing materials: evaluate volume across different board sizes and thicknesses.
- Sheet goods: convert plywood thickness and area into board feet for comparisons.
- Budgeting: estimate cost at different price per BF rates.
Quick Reference Table
These quick references help you sanity-check results. The calculator will compute exact totals, but it’s useful to recognize common volumes.
| Example piece | Calculation | Board feet | Notes |
|---|---|---|---|
| 1″ × 12″ × 1 ft | (1×12×1) ÷ 12 | 1.0 BF | Definition example |
| 1″ × 6″ × 8 ft | (1×6×8) ÷ 12 | 4.0 BF | Common hardwood board |
| 2″ × 6″ × 8 ft | (2×6×8) ÷ 12 | 8.0 BF | Double thickness doubles BF |
| 3/4″ 4×8 sheet | 0.75 × 32 | 24.0 BF | Sheet goods method |
Accuracy Tips
- Use actual sizes whenever possible (especially for “2×” lumber).
- Measure thickness after surfacing if boards are planed.
- Round consistently (e.g., to 1/8″ or 1/16″) if that’s how your yard measures.
- Add waste for cutting, layout, defects, and grain selection.
- For rough lumber, remember that final thickness after planing may be smaller than the rough thickness.
FAQ
Board Foot Calculator – Frequently Asked Questions
Clear answers about board foot formulas, sheet goods, waste factor, and pricing.
A board foot is a lumber volume unit equal to a piece that is 1 inch thick × 12 inches wide × 12 inches long (144 cubic inches). It’s commonly used to price hardwood lumber.
For thickness and width in inches and length in feet: Board Feet = (Thickness × Width × Length) ÷ 12. If length is in inches: Board Feet = (Thickness × Width × Length) ÷ 144.
Board feet provide a consistent way to measure and price irregular or rough-sawn boards by volume, even when boards differ in width and thickness.
No. A linear foot is just length. A board foot is volume and depends on thickness and width as well as length.
Use: Board Feet = Thickness (in) × Area (ft²). For example, a 3/4" 4×8 sheet has area 32 ft² → 0.75 × 32 = 24 board feet.
Nominal size is the name (like 2×4). Actual size is smaller after drying and planing (often 1.5×3.5 inches). Use actual dimensions for accurate board feet.
Many projects use 5–15% waste depending on layout, knots/defects, grain matching, and cutting complexity. This calculator lets you add a waste percentage to plan safely.
Multiply total board feet by the price per board foot. You can also add a waste factor first and price the “with waste” total for a more realistic estimate.
BF is a common abbreviation for board feet. Some yards also use “bd ft” or “bdft.”
Yes. Enter mm/cm/m and the calculator converts to the correct volume internally, then outputs total board feet and helpful conversions.
Differences can happen due to rounding, measuring at the narrowest point, surfacing (S2S/S3S), nominal vs actual sizes, or how the yard grades and tallies boards.