Board Feet Calculator
Calculate board feet of lumber for woodworking, carpentry, or timber projects — add multiple boards at once, get per-board and total board feet, cubic feet, cubic meters, and estimated cost. Also includes a dedicated log board feet calculator using Doyle, Scribner, and International log rules.
Example: (2 in × 6 in × 8 ft) ÷ 12 = 8.00 board feet
If length is in inches: divide by 144 instead of 12.
How to Calculate Board Feet
Board feet is the standard unit for buying and selling lumber in North America. Here is how to calculate it for both cut lumber and whole logs.
Add Your Boards
Click "Add Board" or use the quick-add presets (2×4, 2×6, 1×6, etc.) to add boards to your list. Enter a name, thickness, width, length, and quantity for each. Use actual dimensions — not nominal — for precise results.
Choose Units & Options
Select your preferred length unit (feet, inches, metres, or centimetres). Add a price per board foot for cost estimation. Choose a waste factor (10% is standard for most projects) to account for cuts and defects.
For Logs: Use the Log Tab
Switch to the Log Board Feet tab and enter your log's small-end diameter (inside bark) and length. The calculator shows board feet using three different log rules — Doyle, Scribner, and International — so you can compare estimates.
Read Your Results
See total board feet, cubic feet, cubic metres, MBF (thousand board feet), per-board breakdown, estimated cost, and recommended order quantity with waste factor — all updated live as you type.
Common Lumber Sizes — Nominal vs Actual Dimensions
When calculating board feet, always use actual dimensions — not the nominal name printed on the label. Nominal sizes are what lumber is called; actual sizes are smaller due to drying and planing.
| Nominal Size | Actual Thickness (in) | Actual Width (in) | BF per 8-ft board | Common Use |
|---|---|---|---|---|
| 1×4 | 0.75 | 3.5 | 1.75 | Shelving, trim, panelling |
| 1×6 | 0.75 | 5.5 | 2.75 | Fencing, siding, shelving |
| 1×8 | 0.75 | 7.25 | 3.63 | Wide shelving, panelling |
| 1×12 | 0.75 | 11.25 | 5.63 | Shelving, wide boards |
| 2×4 | 1.5 | 3.5 | 7.00 | Framing, studs |
| 2×6 | 1.5 | 5.5 | 11.00 | Floor joists, rafters |
| 2×8 | 1.5 | 7.25 | 14.50 | Joists, headers |
| 2×10 | 1.5 | 9.25 | 18.50 | Floor joists, beams |
| 2×12 | 1.5 | 11.25 | 22.50 | Stair stringers, beams |
| 4×4 | 3.5 | 3.5 | 16.33 | Posts, columns |
| 4×6 | 3.5 | 5.5 | 25.67 | Beams, timber framing |
| 6×6 | 5.5 | 5.5 | 40.33 | Heavy posts, timber framing |
Board feet per 8-ft board calculated using actual dimensions: (thickness × width × 8) ÷ 12. Use the calculator above to get exact board feet for any custom length.
Understanding Board Feet — The Complete Guide
A board foot is a unit of lumber volume equal to a piece 1 inch thick, 12 inches wide, and 12 inches long — exactly 144 cubic inches. It is the standard unit for buying and selling lumber in the United States and Canada, and understanding how to calculate board feet is essential for estimating the cost and quantity of lumber for any woodworking or carpentry project.
The board foot formula is: BF = (Thickness in inches × Width in inches × Length in feet) ÷ 12. If your length is measured in inches rather than feet, divide by 144 instead of 12. The formula works for any combination of dimensions — it always produces the volume in board feet as long as thickness and width are in inches.
For logs, calculating board feet is more complex because you are estimating how much usable lumber can be sawn from a round log. Different log rules — Doyle, Scribner, and International — use different assumptions about saw kerf, slabs, and taper to estimate yield. The Doyle rule is most common in the eastern US but significantly underestimates small logs. The International 1/4-inch rule is generally considered the most accurate.
- Use actual dimensions, not nominal — a "2×4" is actually 1.5 × 3.5 inches
- Always add 10–15% waste for cuts, defects, and end trimming
- Lumber is priced per board foot — multiply BF by price for total cost
- MBF (thousand board feet) is the standard unit for large timber orders
- Log diameter is measured inside the bark at the small (narrow) end
- Doyle, Scribner, and International rules give different BF estimates for logs
🌳 Doyle vs Scribner vs International Log Rules
The Doyle Log Rule — formula: ((D−4)² × L) ÷ 16 — is simple and widely used but underestimates board feet in small logs (under 20 inches) and overestimates in very large logs. The Scribner Rule uses published tables based on diagram diagrams of boards in a log cross-section, giving conservative estimates. The International 1/4-inch Rule is the most mathematically accurate, accounting for saw kerf, slabs, and taper — it typically yields values between Doyle and Scribner for most log sizes.
🪓 Hardwood vs Softwood Pricing
Lumber prices vary dramatically by species and grade. Softwood framing lumber (pine, spruce, fir) is typically priced at $2–$6 per board foot. Hardwoods range from $4 per board foot for common species like poplar and red oak to $15+ for premium species like walnut, cherry, or figured maple. Exotic hardwoods can exceed $50 per board foot. Always get current pricing from your local lumber yard — national price indices provide a useful baseline but local variation is significant.
🔧 Waste Factor — Why 10% Is the Standard
Every lumber project generates waste: end cuts, knots and defects to work around, width rip-cuts that leave off-cuts, and boards that split on final assembly. A 10% waste factor is standard for straightforward projects with rectangular cuts. Add 15–20% for complex shapes, curved pieces, or projects with many angled cuts. For finish carpentry where waste is minimized, 5% may suffice. When in doubt, round up to the nearest board — running out of lumber mid-project is always more expensive than having a few extra pieces.
📈 How Lumber Dealers Price Board Feet
Retail lumber yards typically price boards individually with the board-foot cost calculated into a per-piece price. Custom mills and hardwood dealers usually quote by the board foot, often with a minimum order. Wholesale timber orders are priced per MBF (thousand board feet). To convert: if a dealer charges $4.50 per board foot and you need 200 board feet, your cost is $900. At MBF pricing of $4,500/MBF, the same 200 board feet (0.2 MBF) costs $900. Our calculator shows both price formats.
Board Feet Calculator FAQs
Common questions about calculating board feet for lumber and logs.
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About This Board Feet Calculator
This board feet calculator uses the standard volumetric formula: BF = (T × W × L) ÷ 12 (thickness and width in inches, length in feet). Log board feet are calculated using three established log rules: the Doyle Rule (((D−4)² × L) ÷ 16), the Scribner Rule (approximated from standard Scribner Decimal C tables), and the International 1/4-inch Rule (based on the standard two-variable formula). All three log rules measure diameter inside bark at the small end.
Results are for planning and estimation purposes. Actual lumber yield from logs varies based on sawyer skill, equipment, log defects, and taper. For commercial timber transactions, always use a certified log scaler or the official log rule required by your state or provincial regulations. This tool is for informational use only.
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