Lumber Calculator
Calculate total lumber volume and length based on piece dimensions, quantity, and selected measurement units.
Lumber Calculator — Board Feet, Linear Feet & Cost Estimator
One board foot of lumber equals 144 cubic inches (12″ x 12″ x 1″). Enter thickness, width, and length in the calculator above to get board feet, linear feet, and total material cost for any project — deck, frame, fence, or furniture.
Order 10% extra for standard framing projects. Order 15% extra for decks with diagonal layouts — angle cuts at board ends waste significantly more material. |
How to Use the Lumber Calculator
To get a lumber estimate, enter 4 values: thickness (in), width (in), length (ft), and quantity. The calculator returns board feet per piece, total board feet, linear feet, and material cost.
- Enter dimensions in nominal size — a 2×4 is actually 1.5″ x 3.5″; use nominal values for board foot calculations
- Enter quantity — total number of boards needed for the project
- Select wood species — pricing varies from .50/BF for pine to 5+/BF for walnut and teak
- Adjust waste factor — 10% for framing, 15% for decks, 20% for herringbone and diagonal patterns
- Read results — board feet, linear feet, total board count, and purchase cost
Board Foot Formula
Board Feet = (Thickness (in) x Width (in) x Length (ft)) / 12 — this is the standard formula used at every lumber yard in the US and Canada.
Worked Example 1 — Single Board
Calculate board feet for one piece of 2×6 lumber at 8 feet long:
- (2 x 6 x 8) / 12 = 8 board feet per piece
Worked Example 2 — Full Project
Calculate total board feet for 20 pieces of 2×4 at 12 feet long:
- One piece: (2 x 4 x 12) / 12 = 8 BF per board
- 20 pieces: 20 x 8 = 160 board feet total
- With 10% waste: 160 x 1.10 = 176 BF to order
Nominal vs Actual Lumber Dimensions
Lumber is sold in nominal sizes but cut to smaller actual dimensions — the mill planes and dries the board after cutting. Always use nominal dimensions for board foot calculations.
Nominal Size | Actual Size | Board Feet per LF | Common Use |
1×4 | 0.75″ x 3.5″ | 0.33 BF/LF | Trim, shelving, furring |
1×6 | 0.75″ x 5.5″ | 0.50 BF/LF | Fencing, siding, decking |
2×4 | 1.5″ x 3.5″ | 0.67 BF/LF | Wall framing, studs |
2×6 | 1.5″ x 5.5″ | 1.00 BF/LF | Floor joists, rafters, decks |
2×8 | 1.5″ x 7.25″ | 1.33 BF/LF | Floor joists, deck beams |
2×10 | 1.5″ x 9.25″ | 1.67 BF/LF | Long-span joists, headers |
2×12 | 1.5″ x 11.25″ | 2.00 BF/LF | Stair stringers, large beams |
4×4 | 3.5″ x 3.5″ | 1.33 BF/LF | Fence posts, deck posts |
6×6 | 5.5″ x 5.5″ | 3.00 BF/LF | Deck posts, structural columns |
Lumber Cost by Wood Species
These are 2026 US average prices for S4S (surfaced 4 sides) dimensional lumber:
Wood Species | Cost per BF | Best Use | Durability |
Pressure-Treated Pine | /bin/sh.80-.50 | Decks, outdoor framing | High — treated for rot/insects |
Douglas Fir | .00-.00 | Structural framing, beams | High — strong, straight grain |
Southern Yellow Pine | /bin/sh.80-.80 | Framing, subfloor | Medium-High — hard softwood |
Cedar (Western Red) | .00-.00 | Decks, fencing, siding | Very High — natural rot resistance |
Redwood | .00-.00 | Outdoor decks, furniture | Very High — premium outdoor wood |
White Oak | .00-0.00 | Furniture, flooring, cabinets | Very High — hard, dense |
Hard Maple | .00-1.00 | Workbenches, cutting boards | Very High — hardest domestic species |
Walnut | 0.00-8.00 | Fine furniture, tabletops | High — premium hardwood |
Lumber Waste Factors by Project
Project Type | Waste Factor | Reason |
Wall framing (studs) | 10% | Standard cuts at top and bottom plates |
Floor joists | 10% | Minimal cuts — joists run full span |
Roof rafters | 15% | Bird’s mouth cuts and ridge cuts |
Deck boards (straight) | 10% | End cuts only at perimeter |
Deck boards (diagonal) | 15% | Angle cuts at all 4 edges |
Fence boards | 10% | Height cuts and post notches |
Hardwood furniture | 20-25% | Defect removal and grain matching |
Herringbone pattern | 25% | Maximum waste — 45 degree cuts every board |
Linear Feet vs Board Feet — When to Use Each
Use board feet when pricing and buying lumber by volume. Use linear feet when measuring trim or molding. Use square feet when planning surface coverage like decking or paneling.
- Board feet (BF): volume measurement — used for pricing hardwood and structural lumber
- Linear feet (LF): length only — used for trim, baseboard, molding, and railing
- Square feet (SF): area coverage — used for decking, siding, and paneling
- Thousand board feet (MBF): bulk unit — used for commercial and wholesale lumber orders
To convert linear feet to board feet: multiply LF x (thickness in inches x width in inches) / 12. A 10 LF board of 2×6 = 10 x (2 x 6) / 12 = 10 BF.
Lumber Calculator for Specific Projects
Deck Lumber — How Much Do You Need?
A standard 12 x 16 ft deck (192 sq ft) using 2×6 deck boards requires approximately 384 linear feet of 2×6 (32 BF at 10% waste). Use the deck calculator at rainyroofers.com/deck-calculator for a complete material list including joists, posts, and hardware.
Wall Framing — Studs per Linear Foot of Wall
A standard 8-ft wall at 16″ on-center spacing needs 9 studs plus 3 plates per 10 linear feet of wall. Add double studs at each door opening and a header sized to the span.
Fencing — Boards per Linear Foot
A 6-ft privacy fence using 1×6 boards needs 20 fence boards, 2 posts, and 4 rails per 10 linear feet. Apply 10% waste for end cuts. Use PT lumber rated UC4B or higher for posts in direct ground contact.
Frequently Asked Questions
What is a board foot of lumber?
One board foot equals 144 cubic inches of lumber — the volume of a piece 1 foot long, 1 foot wide, and 1 inch thick. Board feet are the standard unit for pricing and buying dimensional and hardwood lumber in the US and Canada.
How many board feet are in a 2x4x8?
5.33 board feet. Formula: (2 x 4 x 8) / 12 = 5.33 BF. At .00 per BF, one 8-ft 2×4 costs .33 in material.
What is the difference between nominal and actual lumber size?
Nominal size is the label size; actual size is smaller due to milling. A 2×4 measures 1.5″ x 3.5″ actual. A 2×6 measures 1.5″ x 5.5″. Nominal sizes affect spacing calculations for decking gaps and stud layouts.
How much does a board foot of lumber weigh?
Dried softwood weighs 1.5-2.5 lbs per BF. One board foot of dried oak weighs 3.08-4.67 lbs (1.4-2.1 kg). Use rainyroofers.com/concrete-weight-calculator if your project includes both lumber and concrete footings.
How do I calculate lumber for a deck?
Multiply deck length x width to get square feet. Divide by board width (in feet) to get linear feet. Add 10-15% waste. For a 200 sq ft deck using 2×6 boards: 200 / 0.458 = 437 LF + 10% = 481 LF. Use rainyroofers.com/deck-calculator for the complete estimate.
What lumber size is best for deck framing?
Use 2×8 joists for spans up to 12 ft, 2×10 for spans up to 14 ft. Beams use doubled 2×8 or 2×10 boards bolted together. Posts are 6×6 PT lumber for elevated decks
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