Free Board Foot Calculator — Lumber Volume & Cost

How to Use the Board Foot Calculator

How to Calculate Board Feet

A board foot is the standard unit for measuring and pricing hardwood lumber in North America. One board foot equals a piece of wood 1" thick × 12" wide × 12" long — or 144 cubic inches of material. The formula is straightforward: Board Feet = (Thickness × Width × Length) ÷ 144 when all dimensions are in inches, or (Thickness × Width × Length in feet) ÷ 12 when length is measured in feet. For example, a board that is 1" thick, 8" wide, and 10' long contains (1 × 8 × 10) ÷ 12 = 6.67 board feet. Enter your lumber dimensions into this calculator and it handles the math instantly, including multi-board lists and total cost estimation.

Nominal vs. Actual Lumber Dimensions

Lumber is sold by its nominal size but is actually milled smaller after drying and surfacing. Board feet are always calculated from the nominal dimensions — never the actual. This matters because the difference is significant: a nominal 2×4 actually measures 1-1/2" × 3-1/2", and a nominal 1×6 measures 3/4" × 5-1/2". Here are the most common conversions:

• 1× stock: Nominal 1" thick → Actual 3/4" thick
• 2× stock: Nominal 2" thick → Actual 1-1/2" thick
• 4× stock: Nominal 4" thick → Actual 3-1/2" thick
• Width: Nominal 4" → 3-1/2"; Nominal 6" → 5-1/2"; Nominal 8" → 7-1/4"; Nominal 10" → 9-1/4"; Nominal 12" → 11-1/4"

When you purchase a 1×8×10' board at the lumberyard, you pay for 6.67 board feet based on the nominal 1" × 8" × 10' dimensions, even though the actual board measures 3/4" × 7-1/4". This is the universally accepted industry convention.

Quarter-Sawn Notation: 4/4, 5/4, 6/4, 8/4

Hardwood lumber thickness is expressed in quarters of an inch, written as a fraction over four. This notation tells you the rough-sawn thickness before surfacing:

• 4/4 (four-quarter) = 1" rough → approximately 13/16" surfaced
• 5/4 (five-quarter) = 1-1/4" rough → approximately 1-1/16" surfaced
• 6/4 (six-quarter) = 1-1/2" rough → approximately 1-5/16" surfaced
• 8/4 (eight-quarter) = 2" rough → approximately 1-3/4" surfaced
• 12/4 (twelve-quarter) = 3" rough → approximately 2-3/4" surfaced

Board footage is calculated from the rough (quarter) thickness, not the surfaced dimension. A 6/4 board that is 6" wide and 8' long contains (1.5 × 6 × 8) ÷ 12 = 6 board feet.

Rough vs. Surfaced (S4S) Lumber

Rough lumber comes straight from the sawmill with saw marks on all four faces. It is the full nominal thickness and is the most cost-effective way to buy hardwood if you have a planer and jointer. S4S (Surfaced Four Sides) lumber has been planed smooth on both faces and jointed straight on both edges. S4S stock is thinner than the nominal dimension because material is removed during surfacing — typically 3/16" from each face for hardwoods.

Regardless of whether you buy rough or S4S, you pay for the nominal board footage. A 4/4 board is priced at 1" thickness whether it arrives rough at a full inch or surfaced at 13/16". If you buy rough lumber and plan to surface it yourself, factor in the material loss: expect to lose 3/16" to 1/4" of thickness and 1/4" to 3/8" of width during the planing and jointing process.

Hardwood vs. Softwood Pricing

Hardwood lumber (oak, walnut, maple, cherry) is almost always priced per board foot. You will see prices listed as "$X.XX/BF" at hardwood dealers. Softwood lumber (pine, spruce, fir, cedar) sold at home centers is typically priced per linear foot or per piece rather than per board foot. When comparing prices between suppliers, always convert to a common unit — price per board foot is the most reliable comparison for hardwood, while price per linear foot works better for dimensional softwood.

Pro Tips

• Always buy 10–20% more board footage than your cut list requires. Hardwood boards have natural defects — knots, checks, sapwood, and wane edges — that you will need to cut around. The wider and longer the boards, the more flexibility you have for layout.
• Check moisture content before purchasing. Target 6–8% for interior furniture and cabinetry, and 12–15% for exterior projects. Wood that is too wet will shrink, warp, and crack after assembly. A pin-type moisture meter is a small investment that prevents expensive mistakes.
• Random width and length (RWL) hardwood is significantly cheaper than specified-width boards. If your project can accommodate varying widths (tabletops, panels, cutting boards), buying RWL saves 15–30% on material cost.
• If buying rough lumber to plane yourself, add surfacing loss to your thickness requirements. Need a 3/4" finished panel? Start with 4/4 (1") rough stock — you have enough margin at 4/4 for planing and sanding to a 3/4" finished thickness.
• When building a lumber list, group boards by species and thickness to get the best volume pricing. Many hardwood dealers offer quantity discounts starting at 50–100 board feet.