Order cleanly.
Board feet and lineal feet for any lumber order. Handles nominal sizes (2×4, 2×6, etc.) and quantities for framing, decks, and projects.
How we calculated this
Board feet is the standard unit for lumber volume in North America. One board foot equals a piece 1 inch thick, 12 inches wide, and 1 foot long, which is 144 cubic inches of wood. The formula is (nominal thickness × nominal width × length in feet) divided by 12.
Note the 'nominal' in that formula. A 2×4 is actually 1.5 × 3.5 inches after milling, but board-foot calculations use the nominal dimensions (2 × 4) to keep things consistent across rough and dressed lumber. This is how lumber has been sold for over a century.
Lineal feet is the simpler measurement, the total length of lumber regardless of cross-section. A 2×4 at 8 feet long is 8 lineal feet. A 2×12 at 8 feet long is also 8 lineal feet. But the 2×12 is 6 board feet versus the 2x4's 5.33 board feet, so the 2×12 costs roughly 12× more per lineal foot.
Waste factor for framing and construction lumber: 0% if you're ordering to a precise pre-calculated list, 10% for typical projects where you're cutting stock to fit. 15% for projects with complex angles or repeated short cuts that leave lots of unusable scrap. Always round up to whole boards. A 10% buffer on 50 boards is 55, not 55.0.
Pricing: lumber yards quote in different units. Big-box retailers usually price per piece ("$5.47 each"). Wholesale lumber yards quote per 1,000 board feet ("$850 MBF"). Convert between them: price per piece ÷ board feet per piece = price per board foot. Multiply by 1,000 for MBF.
Board feet, lineal feet, and pieces: three ways to buy the same wood
Lumber yards sell hardwood by the board foot. Big-box stores sell framing lumber by the piece. Contractors quote in lineal feet. These are three different units for the same material, and mixing them up is the fastest way to order the wrong amount. The calculator above converts between all three, but knowing what each unit means lets you check any quote or cut list before the wood is on the truck.
The board foot is the one people trip over, because it's a unit of volume, not length. A single board foot is a piece one inch thick, twelve inches wide, and twelve inches long, or any shape that adds up to the same 144 cubic inches. Lineal feet just measures length regardless of the board's cross-section, so ten lineal feet of 2×4 and ten lineal feet of 2×12 are the same lineal number but wildly different amounts of wood. Pieces are what the store shelf actually holds. This page and the calculator move between all three.
How to calculate board feet
The formula is thickness times width times length, all in inches, divided by 144. The only trick is that board feet use the nominal dimensions, the numbers on the label (2 and 4 for a 2×4), not the smaller actual milled size. That's a deliberate convention: board feet measure how much wood you're paying for at the sawmill's rough dimension, before planing.
Walk through a 2×4×8. Thickness 2, width 4, length 96 inches (that's the 8 feet). Multiply: 2 times 4 times 96 is 768. Divide by 144 and you get 5.33 board feet. A 2×6×8 is 2 times 6 times 96 over 144, which is 8 board feet. A 1×12×10 (a shelf board) is 1 times 12 times 120 over 144, or 10 board feet. Once the pattern clicks it's quick, and the calculator does it for a whole list at once, but being able to check a single piece by hand keeps a lumber yard from overcharging you on a hardwood order.
How we calculated these numbers▾
Board foot formula: nominal thickness times nominal width times length in inches, divided by 144. Nominal-to-actual conversions follow American Lumber Standards Committee PS 20 and WWPA references. Weight estimates use typical kiln-dried density for SPF (about 2.1 lb per board foot) and green or treated southern yellow pine (about 3.5 to 4.2 lb per board foot). Pricing reflects 2026 retail at Home Depot and Lowe's.
Converting between board feet, linear feet, and square feet
These conversions come up constantly and they confuse people because the units measure different things: linear feet is length, square feet is area, board feet is volume. You can only convert between them if you know the board's dimensions, and that's the step people skip.
Linear feet to board feet needs the thickness and width. A linear foot of 2×6 is (2 times 6 times 12) over 144, or 1 board foot per linear foot, so 40 linear feet of 2×6 is 40 board feet. Linear feet to square feet needs the width: a board that's 5.5 inches wide (an actual 2×6 face) covers 5.5 over 12, or 0.458 square feet per linear foot, so 40 linear feet of it covers about 18.3 square feet of surface. This is the calculation you want when you're figuring how many linear feet of decking or fence board it takes to cover a given area.
Board feet to square feet is the same idea from the other direction: divide the board feet by the thickness in inches to get square feet of one-inch-thick coverage. The reason no single number works for all of these is that a "foot" of lumber means a different quantity depending on which dimension you're holding fixed. The calculator asks for the board size precisely so it can do these conversions correctly instead of guessing.
Nominal sizes are not actual sizes
How much your lumber weighs
Weight matters more than people expect, and not just for the drive home. It decides whether you can carry a piece alone, whether your trailer is over its rating, and how much a stack loads a floor or a truck bed. Weight depends on the species and, heavily, on moisture: green or freshly treated lumber can weigh nearly twice its kiln-dried equivalent because it's full of water.
Board | Kiln-dried SPF | Pressure-treated | |
|---|---|---|---|
| 2×4×8 | ~11 lb | ~17-22 lb | |
| 2×6×8 | ~17 lb | ~28-34 lb | |
| 2×8×8 | ~22 lb | ~36-44 lb | |
| 4×4×8 | ~22 lb | ~36-44 lb | |
| Per board foot | ~2.1 lb | ~3.5-4.2 lb |
Pressure-treated lumber is heavy because it is often still wet with treatment chemicals when you buy it. A treated 2x8x8 is a genuine two-person lift. Weights drop as treated lumber dries over the following weeks.
A practical rule: kiln-dried framing SPF runs about 2 pounds per board foot, and wet pressure-treated stock runs closer to 4. So a bunk of treated deck joists weighs about double what the same count of dry SPF studs would, which is worth knowing before you rent a trailer or plan to carry it upstairs.
Species: what to use where
SPF (framing) | Pressure-treated | Cedar/redwood | |
|---|---|---|---|
| Use | Interior walls, roof framing | Deck, fence, ground contact | Outdoor furniture, siding, trim |
| Relative cost | 1× (baseline) | 1.5-2× SPF | 2-4× SPF |
| Ground contact OK? | No (rots within 2 yr) | Yes (chemical treatment) | Yes (natural oils, limited) |
| Paintable? | Yes | After 6 months cure | Yes (or leave natural) |
SPF is for anything that stays dry. PT is for anything exposed to weather or ground. Cedar is the premium natural option for looks.
What lumber costs, and when to buy
Composite illustration based on typical project dimensions, regional contractor pricing, and 2026 material costs. Not a specific real project.
Buying at a lumberyard versus a big-box store
Where you buy changes the unit you're quoted in and the quality you get, and it's worth knowing before you show up with a list. Big-box stores (Home Depot, Lowe's) sell framing lumber by the piece at a marked shelf price, which is convenient for small jobs and lets you hand-pick boards, though the picked-over bins mean more culling. A dedicated lumberyard sells by the board foot, especially for hardwoods and better softwood grades, and will quote a whole tally at once. For a big framing order the yard is usually cheaper per board foot and the stock is straighter, but you need to speak their unit, which is board feet, not pieces.
Hardwoods are almost always sold by the board foot and often in random widths and lengths, so the board-foot math on this page is exactly how you check a hardwood quote. A quote of "40 board feet of red oak at $6" is $240, and knowing that a 1×6×8 oak board is 4 board feet lets you sanity-check how many boards that is (ten of them). Walking in able to do that conversion is the difference between taking the counter's word and knowing your order.
Board feet versus square feet, and when each matters
These two get conflated because both sound like "how much wood," but they answer different questions. Board feet measures volume, what you pay for, and it's the right unit for pricing and for structural stock where thickness matters. Square feet measures surface area, what you cover, and it's the right unit for decking, flooring, siding, and paneling where you care about the face, not the thickness.
A concrete case: for a deck surface you think in square feet of decking to cover the frame, but you buy the decking boards in linear or board feet, so you convert. A 5/4×6 deck board (actual face about 5.5 inches) covers roughly 0.46 square feet per linear foot, so a 200-square-foot deck needs about 435 linear feet of board before waste. Get the unit wrong here and you either strand yourself short or haul back an extra bunk. The calculator keeps the units straight so you order the right amount the first time.
Where lumber orders go wrong
Calculating coverage from nominal size. The big one. Framing a wall or laying out decking using 2 inches by 4 inches instead of 1.5 by 3.5 throws off every spacing and coverage number. Use nominal only for board-foot pricing; use actual for fit.
Confusing lineal feet with board feet. Ordering "40 feet of 2×6" is ambiguous. If the yard reads it as board feet and you meant lineal, you get far less wood than you planned. State the unit every time.
Forgetting the waste factor. Every cut list generates offcuts, and some boards arrive crowned, split, or twisted and go straight to the cull pile. Add about 10 percent to framing lumber and 15 percent to trim and finish stock, where appearance rules out more pieces.
Ignoring moisture weight. People rent a trailer for the piece count, not the weight, and discover treated lumber is nearly double what they estimated. Check the weight before you load.
For framing projects, pair this calculator with the stud spacing calculator for wall layouts and the stair calculator for stringer sizing. For a deck, the deck calculator handles joist and beam sizing directly, and the board-foot math here tells you what that framing costs.
Frequently asked
What is a board foot?
One board foot equals a piece of lumber 1 inch thick, 12 inches wide, and 1 foot long. That's 144 cubic inches of wood. Board feet is the standard way to measure and sell lumber volume in the US and Canada, and it accounts for cross-section (thickness × width) and length together.
Why is a 2×4 not actually 2 by 4 inches?
The '2×4' is the nominal (rough) dimension before milling. When lumber is dried and planed smooth, it loses about 1/2 inch from thickness and width. Finished: 1.5 × 3.5 inches. This has been the industry standard since the 1920s. Board-foot math still uses nominal dimensions for consistency.
How do I convert lineal feet to board feet?
Multiply lineal feet by nominal thickness and width, divide by 12. For a 2×6: lineal × 2 × 6 ÷ 12 = lineal × 1. So 10 lineal feet of 2×6 = 10 board feet. For 1×4: lineal × 1 × 4 ÷ 12 = lineal × 0.33. So 10 lineal feet of 1×4 = 3.33 board feet.
How much lumber do I need for a deck?
For deck materials specifically, use the deck calculator, which factors in decking boards, joists, beams, posts, and fasteners. The lumber calculator here is for general framing or when you need to compute board feet for cost comparison or bulk ordering.
What's the difference between cheap and premium lumber?
Grade. Cheap lumber ('stud grade' or 'no. 2') has knots, slight warping, and visible wane. Premium lumber ('select structural' or 'no. 1') has fewer defects and is straighter. Cost difference is 30-100%. For hidden framing, stud grade is fine. For exposed work (furniture, trim), premium is worth it.
How much does lumber cost?
Extremely volatile in recent years. Roughly: 8-foot 2×4 stud grade SPF = $4-8; 16-foot 2×10 = $25-45; 8-foot 4×4 pressure-treated = $15-25. Pressure-treated costs 50-100% more than untreated. Prices swing 30-50% seasonally and with housing market cycles.
Should I buy pressure-treated or regular lumber?
Pressure-treated (PT) for anything in contact with ground, concrete, or outdoors without protection: fence posts, deck framing, ledger boards, sill plates. Regular lumber for interior framing, visible deck boards (can use PT but it splits and warps more), and furniture. Cedar and redwood are rot-resistant naturally but cost 2-3× more than PT.
What are MBF and M in lumber pricing?
MBF = thousand board feet (Roman M = 1,000). Lumber wholesale is quoted per MBF: '$850/MBF' means $0.85 per board foot. A single 2×4×8' board is 5.33 bf, so at $850/MBF it's $4.53 per piece. Retail stores usually quote per piece directly; wholesale and contractor pricing use MBF.
Sources
- American Lumber Standards Committee: PS 20 American Softwood Lumber Standard - The federal standard defining nominal versus actual softwood lumber dimensions
- Western Wood Products Association: Board Foot Calculation - Industry reference for the board-foot formula and lumber tallies
- AWC National Design Specification for Wood Construction - Species design values and structural properties for framing lumber
- USDA Forest Products Laboratory: Wood Handbook - Wood density and moisture data behind the weight estimates in this guide
- Southern Forest Products Association: Pressure-Treated Lumber - Treatment retention levels and ground-contact ratings for southern yellow pine
Was this calculator helpful?