Calculate-Compare-Decide
Calculate board feet for any lumber from its thickness, width and length — with hardwood quarter sizes, dimensional lumber presets, and the nominal-versus-actual difference shown side by side so you know exactly what you're paying for. Get volume, species weight, cut lists and cost as you type.
Everything updates live — the board drawing too.
Estimate from your inputs. Lumber sizes and pricing vary by supplier — confirm before ordering.
Board feet = (thickness in inches × width in inches × length in inches) ÷ 144. If the length is in feet, divide by 12 instead. One board foot is a piece 1 in thick, 12 in wide and 12 in long — 144 cubic inches. A 2×4 × 8 ft is 5.33 board feet using nominal size. Lumber is billed on nominal dimensions, not the smaller actual size you receive.
Five steps. The board drawing and both nominal and actual figures update as you type.
Nominal is the size lumber is sold and billed as; actual is what you measure. The calculator shows both regardless, so you can see the difference.
Use the 2×4-style presets for construction lumber, or the quarter presets (4/4, 8/4) for hardwood sold by thickness.
Length has its own unit selector because boards are almost always sold in feet while thickness and width are in inches.
Species sets the density so you get a realistic weight, adjusted for moisture content — green lumber can weigh a third more than kiln dried.
Set a waste allowance for defects and offcuts, enter the price per board foot, then copy, share, print or export the result.
The board foot is a volume unit, not an area unit. Everything below follows from that one idea.
Why 144 and 12? A board foot is 144 cubic inches. Dividing inches³ by 144 gives board feet. If you leave the length in feet, you have already divided one dimension by 12, so you only divide by the remaining 12.
Which do you use? Softwood construction lumber is bought and billed by nominal size, so a 2×4 is charged as 5.33 BF even though it delivers 3.5 BF of wood. Rough-sawn hardwood is measured at its rough thickness before surfacing — a 4/4 board planed to 13/16 in is still sold as 4/4. Use nominal for pricing, actual for calculating how much wood you will actually have.
Example — 10 pieces of 2×4 × 8 ft Douglas fir: each is 2 × 4 × 8 ÷ 12 = 5.33 BF, so ten pieces are 53.3 BF. That is 4.44 ft³ of wood which, at 32 lb/ft³ air dried, weighs about 151 lb. With 15% waste you would buy 61.3 BF.
Real project quantities with board feet and weight, calculated with the same formulas as the tool above. Weights assume air-dried lumber.
| # | Project | Lumber | Species | Qty | BF each | Total | Weight |
|---|---|---|---|---|---|---|---|
| 1 | Hardwood flooring | 3/4 × 5 in × 8 ft | Red oak | 40 | 2.50 | 100.0 BF | 367 lb |
| 2 | Deck boards | 5/4 × 6 in × 12 ft | Cedar | 24 | 7.50 | 180.0 BF | 345 lb |
| 3 | Fence boards | 1 × 6 in × 6 ft | Cedar | 50 | 3.00 | 150.0 BF | 288 lb |
| 4 | Cabinet face frames | 4/4 × 3 in × 8 ft | Hard maple | 12 | 2.00 | 24.0 BF | 88 lb |
| 5 | Cabinet door stock | 4/4 × 6 in × 8 ft | Cherry | 10 | 4.00 | 40.0 BF | 117 lb |
| 6 | Shelving | 4/4 × 12 in × 8 ft | Poplar | 6 | 8.00 | 48.0 BF | 116 lb |
| 7 | Pine studs (2×4) | 2 × 4 in × 8 ft | Pine | 50 | 5.33 | 266.7 BF | 556 lb |
| 8 | Wall plates (2×4) | 2 × 4 in × 12 ft | Pine | 20 | 8.00 | 160.0 BF | 333 lb |
| 9 | Floor joists (2×10) | 2 × 10 in × 16 ft | Douglas fir | 18 | 26.67 | 480.0 BF | 1,280 lb |
| 10 | Roof rafters (2×8) | 2 × 8 in × 14 ft | Douglas fir | 22 | 18.67 | 410.7 BF | 1,095 lb |
| 11 | Oak boards | 4/4 × 8 in × 10 ft | Red oak | 15 | 6.67 | 100.0 BF | 367 lb |
| 12 | Thick oak (8/4) | 8/4 × 8 in × 10 ft | White oak | 8 | 13.33 | 106.7 BF | 418 lb |
| 13 | Walnut slab | 8/4 × 20 in × 8 ft | Walnut | 2 | 26.67 | 53.3 BF | 169 lb |
| 14 | Walnut boards | 4/4 × 7 in × 8 ft | Walnut | 12 | 4.67 | 56.0 BF | 177 lb |
| 15 | Table top stock | 6/4 × 10 in × 8 ft | Hard maple | 6 | 10.00 | 60.0 BF | 220 lb |
| 16 | Table legs | 12/4 × 4 in × 3 ft | Cherry | 4 | 3.00 | 12.0 BF | 35 lb |
| 17 | Timber beam | 6 × 8 in × 16 ft | Douglas fir | 4 | 64.00 | 256.0 BF | 683 lb |
| 18 | Post (6×6) | 6 × 6 in × 10 ft | Cedar | 6 | 30.00 | 180.0 BF | 345 lb |
| 19 | Bookcase sides | 4/4 × 11 in × 6 ft | Birch | 4 | 5.50 | 22.0 BF | 79 lb |
| 20 | Drawer sides | 1/2 × 5 in × 6 ft | Poplar | 16 | 1.25 | 20.0 BF | 48 lb |
| 21 | Crown moulding stock | 5/4 × 5 in × 12 ft | Poplar | 10 | 6.25 | 62.5 BF | 151 lb |
| 22 | Window trim | 4/4 × 4 in × 8 ft | Pine | 24 | 2.67 | 64.0 BF | 133 lb |
| 23 | Bench seat | 8/4 × 12 in × 6 ft | Teak | 3 | 12.00 | 36.0 BF | 123 lb |
| 24 | Cutting boards | 8/4 × 6 in × 4 ft | Hard maple | 5 | 4.00 | 20.0 BF | 73 lb |
| 25 | Guitar body blanks | 8/4 × 8 in × 2 ft | Mahogany | 4 | 2.67 | 10.7 BF | 33 lb |
| 26 | Bed frame rails | 6/4 × 6 in × 7 ft | Cherry | 4 | 5.25 | 21.0 BF | 61 lb |
| 27 | Workbench top | 8/4 × 4 in × 8 ft | Hard maple | 10 | 5.33 | 53.3 BF | 196 lb |
| 28 | Metric board (50×150 mm) | 50 × 150 mm × 3 m | Pine | 20 | 9.53 | 190.7 BF | 397 lb |
| 29 | Metric beam (100×200 mm) | 100 × 200 mm × 4 m | Douglas fir | 6 | 33.90 | 203.4 BF | 542 lb |
| 30 | Metric slab (60×400 mm) | 60 × 400 mm × 2.4 m | Walnut | 2 | 24.41 | 48.8 BF | 155 lb |
Board footage uses the dimensions as listed. Softwood entries use nominal sizes as they are billed; hardwood entries use rough thickness in quarters. Add your waste allowance before ordering.
What the numbers mean at the lumberyard counter.
Hardwood is priced per board foot, so this is the number that determines what you pay. Ask whether the quote is on rough or surfaced dimensions — it changes the total.
A 2×4 is billed as 2×4 but measures 1½×3½. That is a 34% gap. Neither figure is wrong; they answer different questions.
Species density varies more than threefold between cedar and hickory, and green lumber can weigh a third more than kiln dried. Check before loading a vehicle.
Rough hardwood needs 15–30% extra for jointing, planing, defects and cutting to length. Dimensional softwood needs far less.
Both charts recalculate from your current board footage.
What your lumber volume weighs in each species, at your moisture setting.
How much wood you are billed for compared with what the board actually contains.
Most projects need several different board sizes. Add each one for a combined board-foot total and cost.
Enter the pieces you need and the stock length you can buy. This works out the fewest boards required and shows how to cut each one, allowing for saw kerf.
Uses first-fit-decreasing packing — a good practical solution, though not always the mathematical optimum. Always dry-fit your cut plan before cutting.
Softwood dimensional lumber shrinks when it is dried and surfaced, but keeps its nominal name. These are the standard surfaced-dry sizes in the US.
| Nominal | Actual (in) | Actual (mm) | BF per foot (nominal) | BF per foot (actual) |
|---|---|---|---|---|
| 1 × 2 | ¾ × 1½ | 19 × 38 | 0.167 | 0.094 |
| 1 × 4 | ¾ × 3½ | 19 × 89 | 0.333 | 0.219 |
| 1 × 6 | ¾ × 5½ | 19 × 140 | 0.500 | 0.344 |
| 1 × 8 | ¾ × 7¼ | 19 × 184 | 0.667 | 0.453 |
| 1 × 10 | ¾ × 9¼ | 19 × 235 | 0.833 | 0.578 |
| 1 × 12 | ¾ × 11¼ | 19 × 286 | 1.000 | 0.703 |
| 2 × 4 | 1½ × 3½ | 38 × 89 | 0.667 | 0.438 |
| 2 × 6 | 1½ × 5½ | 38 × 140 | 1.000 | 0.688 |
| 2 × 8 | 1½ × 7¼ | 38 × 184 | 1.333 | 0.906 |
| 2 × 10 | 1½ × 9¼ | 38 × 235 | 1.667 | 1.156 |
| 2 × 12 | 1½ × 11¼ | 38 × 286 | 2.000 | 1.406 |
| 4 × 4 | 3½ × 3½ | 89 × 89 | 1.333 | 1.021 |
| 6 × 6 | 5½ × 5½ | 140 × 140 | 3.000 | 2.521 |
Sizes for surfaced dry softwood. Rough-sawn and green lumber run closer to nominal, and hardwood uses the quarter system instead. Boards 6 in and wider lose ¾ in rather than ½ in.
Density drives weight and is a decent proxy for hardness and workability. Figures are for air-dried wood at roughly 12% moisture.
| Species | Type | Density (lb/ft³) | Weight per BF | Typical use |
|---|---|---|---|---|
| Balsa | Hardwood | 9 | 0.8 lb | Models, cores, buoyancy |
| Cedar (western red) | Softwood | 23 | 1.9 lb | Decking, siding, outdoor |
| Pine (eastern white) | Softwood | 25 | 2.1 lb | Trim, shelving, general |
| Spruce | Softwood | 28 | 2.3 lb | Framing, soundboards |
| Poplar | Hardwood | 29 | 2.4 lb | Paint-grade, drawer sides |
| Douglas fir | Softwood | 32 | 2.7 lb | Framing, beams, structural |
| Plywood | Panel | 34 | 2.8 lb | Sheathing, cabinet carcases |
| Cherry | Hardwood | 35 | 2.9 lb | Furniture, cabinetry |
| Mahogany | Hardwood | 37 | 3.1 lb | Furniture, boatbuilding |
| Walnut | Hardwood | 38 | 3.2 lb | Fine furniture, gunstocks |
| OSB | Panel | 40 | 3.3 lb | Sheathing, subfloor |
| Teak | Hardwood | 41 | 3.4 lb | Marine, outdoor furniture |
| Ash | Hardwood | 42 | 3.5 lb | Tool handles, furniture |
| Birch | Hardwood | 43 | 3.6 lb | Plywood, cabinetry |
| Red oak | Hardwood | 44 | 3.7 lb | Flooring, furniture, trim |
| Hard maple | Hardwood | 44 | 3.7 lb | Worktops, flooring, cutting boards |
| MDF | Panel | 47 | 3.9 lb | Paint-grade panels, jigs |
| White oak | Hardwood | 47 | 3.9 lb | Flooring, barrels, boatbuilding |
| Hickory | Hardwood | 51 | 4.3 lb | Handles, flooring, smoking |
Density varies within a species by growing conditions and moisture. Green lumber can weigh 30–40% more than the air-dried figures shown.
A board foot is a unit of lumber volume, not area. One board foot is the amount of wood in a piece one inch thick, twelve inches wide and twelve inches long — 144 cubic inches, or one twelfth of a cubic foot. It is the standard way hardwood is bought and sold across North America, and it exists because lumber comes in wildly varying widths and lengths. Pricing by volume lets a yard quote one number per species and grade regardless of whether a board is four inches wide or fourteen.
The key thing to understand is that thickness matters as much as face size. A piece 2 inches thick, 6 inches wide and 12 inches long is exactly the same board footage as a piece 1 inch thick, 12 inches wide and 12 inches long — both contain 144 cubic inches of wood.
The board foot dates from an era when sawmills cut to rough dimensions and sold by the volume of timber sawn. Because a mill's cost is driven by the log volume it processes rather than by the finished surface it produces, volume-based pricing matched the economics of the business. That logic survives today in the convention that hardwood is measured at its rough thickness even after it has been surfaced — you pay for the wood the mill cut, not the wood that survived the planer.
Multiply thickness in inches by width in inches by length in inches, then divide by 144. If the length is in feet — which is how boards are usually sold — divide by 12 instead, because one of the twelves is already accounted for. Both routes give the same answer, and the second is faster for the common case of a board quoted as "eight footer".
For multiple identical boards, calculate one board and multiply by the quantity. For a mixed pile, calculate each size separately and add them up, which is what the project lumber list on this page does.
This is the single most confusing thing about buying lumber, and the source of most estimating errors. A board called a "2×4" measures 1½ by 3½ inches. It was genuinely 2 by 4 inches when it was rough-sawn and green, but drying shrinks it and surfacing planes it, and the industry kept the original name. The pattern is consistent: nominal dimensions under 2 inches lose a quarter inch, dimensions from 2 to 6 inches lose a half inch, and dimensions of 8 inches and above lose three quarters.
So which do you use for board feet? For softwood construction lumber, the yard bills you on nominal size — a 2×4×8 is sold as 5.33 board feet even though it contains only 3.5 board feet of actual wood. For estimating cost, use nominal. For working out whether you have enough material for a glue-up or a tabletop, use actual. This calculator shows both so you never have to guess which one a quote is based on.
Hardwood thickness is quoted in quarters of an inch. A 4/4 board (spoken "four quarter") is one inch thick in the rough; 5/4 is 1¼ inch; 6/4 is 1½; 8/4 is 2 inches; 12/4 is 3 inches. Once a 4/4 board has been surfaced on two faces it typically finishes around 13/16 inch, but it is still sold and billed as 4/4. If you need a full inch of finished thickness, you must buy 5/4 and plane it down.
Hardwood widths are usually random rather than standardised, because a mill saws boards to whatever width the log yields. That is why a hardwood order is tallied board by board rather than counted, and why the ability to total a mixed list quickly is genuinely useful at the counter.
Measure thickness at the thinnest point if the board is rough and uneven, since that is what you can actually work with. Measure width at the narrowest point for the same reason, though yards often measure to the nearest inch and may average an irregular board. Length is normally the nominal length; boards are usually cut an inch or two over so you have trim allowance.
When tallying a stack, work in board feet per running foot to speed things up. A 4/4 board 6 inches wide is half a board foot per foot of length, so a 10-foot board is 5 board feet. Keeping those per-foot figures in your head makes checking a yard's tally sheet much faster.
The distinction is botanical rather than about actual hardness: hardwoods come from broadleaf deciduous trees and softwoods from conifers. Balsa is technically a hardwood and is softer than any pine. In practice the categories still track the market — hardwoods like oak, maple, walnut and cherry are sold rough by the board foot in random widths for furniture and cabinetry, while softwoods like pine, fir and spruce are sold surfaced in standard dimensional sizes for construction.
That difference in how they are sold matters more for estimating than the wood itself. Hardwood pricing is per board foot and rises steeply with thickness and width; softwood pricing is often per piece for a standard size, even though it is nominally board-foot based.
Plywood, MDF and OSB are sold by the sheet, not by the board foot, because they come in a standard 4 by 8 foot format. You can still convert if you need to compare — a ¾ inch 4×8 sheet is 0.75 × 48 × 96 ÷ 144 = 24 board feet — but nobody prices it that way. Sheet goods also have their own nominal quirk: a sheet sold as ¾ inch is often 23/32, and ½ inch is often 15/32, which matters when you are cutting joinery.
Wood weight depends heavily on how wet it is. Freshly sawn green lumber can hold more moisture than the weight of the wood fibre itself, and typically weighs 30 to 40 percent more than the same board kiln dried. Kiln dried stock sits at roughly 6 to 8 percent moisture for interior work; air dried lumber settles around 12 percent depending on climate. This calculator adjusts weight for the moisture setting you choose, which matters when you are working out whether a load will fit in a vehicle.
Moisture also drives movement. Wood shrinks and swells across the grain as it gains and loses moisture, so lumber for interior furniture should be acclimatised to the room it will live in before you mill it to final dimensions.
Hardwood grading under the National Hardwood Lumber Association system is based on how much clear, defect-free material a board will yield. FAS (Firsts and Seconds) is the top grade with long clear cuttings, followed by Select, then No. 1 Common — often called cabinet grade because it yields plenty of shorter clear pieces at a much lower price. For projects made of small parts, No. 1 Common is frequently better value than FAS, since you are cutting around defects anyway.
Softwood grading works differently, focusing on structural strength for framing lumber and appearance for finish grades. Grade affects both price and how much waste you should allow.
Multiply total board feet by the price per board foot, and remember to ask whether the quote is based on rough or surfaced dimensions and whether surfacing is included. Many yards charge extra for planing, straight-line ripping and moulding. For softwood, compare the per-piece price to the board-foot equivalent, since a "stud" price is often better than the board-foot rate for the same wood.
Rough hardwood needs the largest allowance: 15 to 30 percent depending on grade, because you lose material jointing one face flat, planing to thickness, ripping an edge straight, and cutting around knots and checks. Surfaced softwood in standard sizes needs far less, often 5 to 10 percent for offcuts. Projects with many short parts waste more than projects with long runs, and figured or highly patterned stock wastes more still because you are selecting for appearance.
The questions people ask most about board feet and buying lumber. Tap any question to expand.