Board Feet Calculator
Free board feet calculator. Instantly calculate lumber volume and cost. Enter thickness, width, length, and quantity for accurate estimates.
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Enter board dimensions and quantity to see results.
About this calculator
How to Calculate Board Feet
Measuring Tips
- Measure thickness and width in inches, length in feet
- Use actual dimensions, not nominal sizes (a 2x4 is actually 1.5x3.5)
- Round up to the nearest inch for rough lumber
- For tapered boards, average the widths at both ends
- Always add 10-15% for waste and defects
Common Lumber Sizes
| Nominal | Actual | BF per 8ft |
|---|---|---|
| 1x4 | 0.75x3.5 | 2.33 |
| 1x6 | 0.75x5.5 | 3.67 |
| 2x4 | 1.5x3.5 | 4.67 |
| 2x6 | 1.5x5.5 | 7.33 |
| 2x8 | 1.5x7.25 | 9.67 |
Tips for Buying Lumber
- Inspect each board for warping, cupping, and defects
- Buy extra for waste, especially with hardwoods
- Consider moisture content for your project type
- Hardwood is sold by the board foot, softwood by the piece
- Prices vary significantly between rough and surfaced lumber
Board Feet Formula Explained
A board foot is a unit of lumber volume equal to a board that is 1 inch thick, 12 inches wide, and 1 foot long (144 cubic inches). It is the standard measurement used to price and sell hardwood lumber in North America. Understanding how to calculate board feet is essential for anyone buying lumber for woodworking, cabinetry, or construction.
The Board Foot Formula
The basic formula multiplies the three dimensions and divides by 12:
Board Feet = (Thickness in inches x Width in inches x Length in feet) / 12
For multiple boards of the same size, multiply the single-board result by the quantity:
Total Board Feet = Board Feet per Piece x Quantity
Example calculation: You need 20 pieces of 2x6 lumber, each 10 feet long. Using actual dimensions (1.5 inches thick x 5.5 inches wide): Board Feet per Piece = (1.5 x 5.5 x 10) / 12 = 6.875 bf. Total = 6.875 x 20 = 137.5 board feet. At $6.00 per board foot for oak, the cost would be $825.00.
Alternative Formula (All Inches)
If you measure length in inches instead of feet, divide by 144 instead of 12:
Board Feet = (Thickness in inches x Width in inches x Length in inches) / 144
This form is useful when working with short pieces. For example, a piece of walnut that is 2 inches thick, 6 inches wide, and 18 inches long: (2 x 6 x 18) / 144 = 1.5 board feet.
Nominal vs. Actual Lumber Dimensions
One of the most common sources of confusion in lumber calculation is the difference between nominal and actual dimensions. Nominal dimensions are the named size of the lumber (what you ask for at the lumber yard). Actual dimensions are the finished size after the wood has been surfaced (planed smooth).
| Nominal Size | Actual Thickness | Actual Width | BF/ft (Actual) |
|---|---|---|---|
| 1x2 | 0.75" | 1.5" | 0.094 |
| 1x4 | 0.75" | 3.5" | 0.219 |
| 1x6 | 0.75" | 5.5" | 0.344 |
| 2x4 | 1.5" | 3.5" | 0.438 |
| 2x6 | 1.5" | 5.5" | 0.688 |
| 2x8 | 1.5" | 7.25" | 0.906 |
| 2x10 | 1.5" | 9.25" | 1.156 |
| 4x4 | 3.5" | 3.5" | 1.021 |
| 6x6 | 5.5" | 5.5" | 2.521 |
Dimensional lumber (softwood) at big-box stores is typically sold by the piece, not by the board foot. Hardwood lumber, however, is almost always priced by the board foot. Rough-sawn lumber is closer to the nominal dimensions, while surfaced (S4S - surfaced four sides) lumber is planed to the actual dimensions shown above. When purchasing hardwood for fine woodworking, always confirm whether the seller prices by nominal or actual dimensions.
Wood Species Weight Reference
The calculator estimates total lumber weight based on species density values informed by the USDA Forest Products Laboratory Wood Handbook. These values represent average density at approximately 12% moisture content, which is typical for kiln-dried lumber.
| Species | Density (lbs/bf) | Common Uses |
|---|---|---|
| Pine (Southern Yellow) | 2.5 | Framing, decking, general construction |
| Douglas Fir | 2.8 | Structural beams, framing, posts |
| Cedar (Western Red) | 2.0 | Decking, siding, fencing, outdoor projects |
| Poplar (Yellow) | 2.4 | Painted cabinetry, trim, utility projects |
| Cherry | 3.0 | Fine furniture, cabinetry, millwork |
| Walnut (Black) | 3.5 | High-end furniture, gunstocks, veneer |
| Maple (Hard) | 3.8 | Flooring, butcher blocks, workbenches |
| Oak (Red) | 3.9 | Flooring, furniture, cabinets, trim |
Weight estimates are useful for planning transportation and handling. For example, 200 board feet of red oak at 3.9 lbs/bf weighs about 780 pounds, which is approaching the payload capacity of a half-ton pickup truck. Freshly sawn (green) lumber can weigh 50-100% more than kiln-dried lumber due to higher moisture content.
Hardwood Lumber Grades and Pricing
Hardwood lumber is graded based on the amount of clear, usable wood in each board. The National Hardwood Lumber Association (NHLA) grading system determines price tiers. Understanding these grades helps you make cost-effective purchasing decisions.
| Grade | Clear Face | Best For |
|---|---|---|
| FAS (Firsts & Seconds) | 83%+ | Fine furniture, long clear cuts |
| FAS 1-Face | 83%+ one side | Cabinetry, visible panels |
| #1 Common | 66%+ | General furniture, smaller parts |
| #2 Common | 50%+ | Utility projects, cutting boards |
FAS grade typically costs 20-40% more than #1 Common. For projects where you need many small pieces, lower-grade lumber often provides better value. For large tabletops or cabinet doors where you need long, wide clear boards, FAS is worth the premium.
Common Board Feet Calculation Mistakes
- Using nominal dimensions for actual volume: A nominal 2x4 has only 65% of the volume suggested by its name. If you need precise volume calculations for weight or cost, always use actual surfaced dimensions.
- Forgetting the waste factor: Hardwood lumber often contains knots, checks, and warp. Add 15-20% for waste on furniture projects and 10% for rough construction. Buying exactly what the calculator shows with no buffer usually leads to a second trip to the lumber yard.
- Confusing board feet with square feet: A 4x8 sheet of 3/4-inch plywood is 32 square feet but 24 board feet. Board feet measures volume; square feet measures area. This distinction matters when comparing prices between sheet goods and solid lumber.
- Not accounting for milling waste: If you are buying rough-sawn lumber and planing it yourself, you will lose 1/8 to 1/4 inch of thickness. An 8/4 (2-inch) rough board yields about 1-3/4 inches after planing. Buy thicker stock than your finished dimension requires.
- Ignoring moisture content: Green (fresh-cut) lumber shrinks as it dries. A board measured green at 100 board feet may yield only 95 board feet after drying. Buy kiln-dried lumber when precise dimensions matter.
Pro Tips for Contractors and Woodworkers
- Buy long and cut down: It is often more economical to buy longer boards and cut them into shorter pieces than to buy exact lengths. An 8-foot FAS board may yield three clear 24-inch pieces, while three separate 24-inch boards might be a lower grade.
- Check moisture with a meter: For indoor furniture and cabinetry, lumber should be at 6-8% moisture content. For exterior projects, 12-15% is acceptable. Wood that is too wet will shrink and warp after installation. Moisture content values consistent with USDA Forest Products Laboratory recommendations suggest acclimating lumber on-site for at least 72 hours before milling.
- Stack and sticker properly: Store lumber flat with uniform stickers (small spacer boards) between layers to promote even air circulation and prevent warping. Keep lumber out of direct sunlight and away from heat sources.
- Factor in kerf loss: Each saw cut removes approximately 1/8 inch of material (the blade kerf). For projects with many pieces, this adds up. A 4-foot board cut into four 12-inch pieces actually needs 48-3/8 inches of raw material, not 48 inches.
- Price by the board foot, not the piece: When comparing lumber prices between suppliers, always convert to cost per board foot. A 2x4x8 at $5.50 each equals about $1.03/bf (nominal) or $1.57/bf (actual). This apples-to-apples comparison reveals the true cost difference.
Questions
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What is the difference between board feet and linear feet?+
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This calculator provides rough estimates for planning purposes only. Default values are based on general industry reference data. Actual quantities may vary. Always verify with a licensed professional before purchasing materials or beginning construction. Full disclaimer.