Board Feet Calculator
Estimate lumber volume in board feet, plus cubic feet/meters, and optional cost.
Quick guide
- Board feet is a lumber volume unit used for pricing and ordering.
- Use actual thickness/width (not nominal) for the most accurate estimate.
- Add waste for knots, defects, and cuts (often 5-10%).
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- Hardwood is often sold in quarters (4/4, 5/4, 8/4); convert quarters to inches before calculating board feet.
- Rough lumber and surfaced lumber (S2S/S4S) can yield different finished thickness—plan for milling loss if you’ll plane it.
- If you need long, straight, or color-matched boards, plan extra beyond simple cut waste.
Nominal vs actual size matters
Board feet is a volume unit, so thickness and width must be in inches and length in feet. Using nominal sizes instead of actual dimensions can distort estimates.
If you're pricing hardwood or finish lumber, plan extra for defects, cutoffs, and grain matching.
If you're buying rough lumber, remember it may be surfaced (planed) down after purchase. The final thickness can change the real usable board feet.
Quarter system example: 4/4 is roughly 1" thick rough-sawn, but after surfacing you may end up closer to 3/4". If you need a true 1" finished thickness, you may need thicker stock.
Quarters system notes: hardwood thickness is often sold as 4/4 (~1" rough), 5/4 (~1.25" rough), 6/4 (~1.5" rough), and 8/4 (~2" rough). After surfacing (planing), the finished thickness is usually less—plan stock thickness based on the finished size you actually need.
Surfaced terms matter: S2S/S3S/S4S describe how many faces/edges are planed. Surfacing can improve usability but changes actual thickness/width and can change pricing (project dependent).
Yield depends on your cut plan. Short parts can use offcuts, but long continuous parts often force you to buy longer boards and cut around defects.
Waste includes more than saw kerf: checks, splits, knots, twist, and the extra length you trim off to get clean ends all reduce usable footage.
Wide boards can be scarce. If you need wide panels or long, visible runs, you may buy more board feet to allow for selecting boards that match and glue up well.
Softwood dimensional lumber is different from hardwood board-foot pricing. A 2x6 is sold by the piece, not by board feet, but you can still use board feet to compare volume across species and products—just don’t confuse “nominal 2x” sizes with actual dimensions when doing the math.
Worked example: one board that is 1" thick x 6" wide x 8 ft long is (1 x 6 x 8) / 12 = 4 board feet. Ten of those boards is 40 board feet, and then you might add waste for defects and cutoffs depending on how picky you need to be.
Board Feet Calculator
Estimate lumber volume in board feet, plus cubic feet/meters, and optional cost.
Results
- Base board feet
- 40
- Waste buffer (board feet)
- 4
- Board feet
- 44
- Cubic feet
- 3.67
- Cubic meters
- 0.104
How board feet works
- Board feet = (thickness in inches x width in inches x length in feet) / 12.
- Multiply by quantity, then add a waste factor if needed.
- If the seller prices per board foot, multiply board feet by that price.
- If you're mixing lengths, calculate per length group and sum them (it's easy to miscount otherwise).
- If thickness is listed in quarters, convert first (e.g., 6/4 = 1.5").
- If you’re buying surfaced hardwood, use the actual measured thickness/width (or supplier spec) instead of the nominal quarters thickness for a tighter estimate.
- If you have a cut list, calculate board feet per part and sum them, then add extra for defects and grain selection.
Assumptions to double-check
- Nominal lumber sizes (e.g., 2x6) are not the same as actual dimensions.
- Rough-sawn lumber may be thicker and varies by mill.
- Some products are priced per linear foot or per piece instead of board feet.
- Surfacing (S2S/S4S) changes thickness and reduces the final usable size.
- Moisture content and storage affect straightness; you may cull more boards than expected if stock is not flat.
- If your project needs consistent finished thickness, milling loss can be meaningful—plan stock thickness accordingly.
Buying tips
- Confirm the actual dimensions and species/grade with the supplier.
- Confirm whether pricing is per board foot of rough stock or per piece of surfaced lumber; it changes totals.
- For finish work, consider adding extra for grain matching and defects.
- Round up to whole boards and keep a little extra for future repairs.
- If you need wide boards, availability can be limited—call ahead and confirm stock before you design around them.
- Buying longer boards and cutting around defects often improves yield and final appearance.
- If the supplier allows it, select boards in person for straightness and grain—especially for visible furniture and trim.
- If you’re building panels, plan how boards will be ripped and glued; narrower boards can be easier to flatten and match.
Common mistakes to avoid
- Mixing up inches and feet in the formula (divide by 12 at the end).
- Using nominal sizes when the seller prices by actual dimensions.
- Not adding waste for defects and cutoffs, especially for finish work.
- Assuming rough lumber finishes at the same thickness you bought (planing reduces size).
- Forgetting to convert quarters-to-inches correctly, which can throw the total off quickly.
- Buying exact board feet with no allowance for board selection, defects, or matching needs on visible projects.
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Results are estimates for informational purposes only. Always verify measurements and product specifications.