How to Calculate Board Feet: Complete Lumber Measurement Guide

Ever stood at the lumber yard staring at price tags, trying to figure out what you'll actually pay? Board feet calculations seem like a secret code—until you crack it.

Here's the formula upfront:

Board Feet (BF) = (Thickness in inches × Width in inches × Length in feet) ÷ 12

That's it. Once you understand this, hardwood lumber pricing becomes crystal clear.

What Is a Board Foot?

A board foot measures volume—specifically, a piece of wood that's:

• 1 inch thick
• 12 inches wide
• 12 inches (1 foot) long

The 12-inch width standard is why we divide by 12. It converts cubic inches into the board foot unit.

Think of it as 144 cubic inches of wood (1 × 12 × 12 = 144). Any combination of dimensions equaling 144 cubic inches = 1 board foot.

The Board Foot Formula Explained

BF = (T × W × L) ÷ 12

| Variable | What It Means | Unit | |----------|--------------|------| | T | Thickness | inches | | W | Width | inches | | L | Length | feet | | 12 | Conversion factor | — |

Board feet measure volume, not just length. Thickness matters here.

Why divide by 12? We're converting cubic inches to board feet. Since thickness and width are in inches but length is in feet, dividing by 12 standardizes the measurement.

Real Example: Calculate Board Feet Step-by-Step

You find a board at the yard:

• Thickness: 2 inches
• Width: 8 inches
• Length: 10 feet

Step 1: Write the formula

BF = (T × W × L) ÷ 12

Step 2: Insert your measurements

BF = (2 × 8 × 10) ÷ 12

Step 3: Multiply first

2 × 8 × 10 = 160

Step 4: Divide by 12

160 ÷ 12 = 13.33 BF

This board contains 13.33 board feet.

Price Per Board Foot: Real Money Math

If oak sells at $6.50 per board foot:

Cost = 13.33 × $6.50 = $86.65

Now you can verify pricing before checkout and catch errors.

Multiple Board Calculation

Project: Building a table requires 8 boards

Each board: 1.5" thick × 6" wide × 8' long

Per board: (1.5 × 6 × 8) ÷ 12 = 6 BF Total needed: 6 × 8 = 48 BF Cost at $8/BF: 48 × $8 = $384

Lumber Grading Systems

Hardwood lumber grades significantly affect price per board foot.

FAS (Firsts and Seconds)

• Highest quality grade
• 83% clear face (knot-free)
• Boards 6"+ wide, 8'+ long
• Price premium: 100% (base rate)

Select Grade

• Second-best quality
• One face FAS quality
• Price: 85-95% of FAS

No. 1 Common

• 66% clear face
• Suitable for furniture with character
• Price: 60-70% of FAS

No. 2 Common

• 50% clear face
• Rustic appearance, more knots
• Price: 40-50% of FAS

Example pricing (Walnut):

• FAS: $12/BF
• Select: $10/BF
• No. 1 Common: $7.50/BF
• No. 2 Common: $5.50/BF

Choose grade based on project visibility and budget.

Rough vs Surfaced Lumber

Rough Sawn (S-RGH):

• As cut from sawmill
• Full nominal thickness
• Requires planing/sanding
• Calculate at full thickness

Surfaced 2 Sides (S2S):

• Planed on two faces
• Loses ~1/4" thickness
• Smoother, ready to work
• Priced at nominal, calculate at nominal

Surfaced 4 Sides (S4S):

• Planed all four sides
• Loses thickness and width
• Ready to use immediately
• Priced at nominal dimensions

Important: Lumber yards typically charge based on rough dimensions, even for surfaced lumber. A 4/4 board (1" rough) surfaced to 3/4" still prices as 1" thick.

Hardwood vs Softwood Pricing Differences

Hardwood (Deciduous Trees)

• Sold by board foot
• Higher price per BF ($3-$20+)
• Varying widths and lengths
• Examples: Oak, maple, cherry, walnut

Softwood (Coniferous Trees)

• Often sold by linear foot or per piece
• Lower cost ($0.50-$3/BF equivalent)
• Standard dimensions (2×4, 2×6, etc.)
• Examples: Pine, fir, cedar, spruce

Why the difference? Hardwood grows slower, comes in random widths, requires careful milling. Softwood grows faster, mills to standard sizes, used for construction framing.

Board Feet Pricing by Wood Species

Budget Hardwoods ($3-$6/BF)

• Poplar: $3.50/BF - Paint-grade, easy to work
• Red Oak: $4.50/BF - Durable, prominent grain
• Soft Maple: $5.00/BF - Light color, fine grain

Mid-Range Hardwoods ($6-$10/BF)

• Cherry: $7.50/BF - Darkens with age, premium look
• Hard Maple: $8.00/BF - Very hard, light color
• White Oak: $8.50/BF - Water-resistant, classic

Premium Hardwoods ($10-$15/BF)

• Walnut: $12.00/BF - Dark chocolate color, luxury
• Mahogany: $13.00/BF - Reddish-brown, stable
• Figured Maple: $14.00/BF - Decorative grain patterns

Exotic Hardwoods ($15+/BF)

• Brazilian Cherry: $16/BF - Extremely hard, deep red
• Teak: $22/BF - Weather-resistant, oily
• Ebony: $100+/BF - Nearly black, rare, dense

Prices vary by region, availability, and grade. These are 2026 averages.

Tally Systems Used in Lumber Yards

Doyle Scale

• Old measurement system
• Underestimates volume of small logs
• Still used in some regions

Scribner Scale

• More accurate than Doyle
• Common in U.S. lumber industry

International 1/4-Inch Scale

• Most accurate modern system
• Used by USDA Forest Service

For buyers: These affect how lumber yards inventory raw logs. Your board foot calculation at purchase uses the standard formula regardless.

Bulk Buying Strategies

Volume Discounts

• 100-499 BF: Typical list price
• 500-999 BF: 5-10% discount
• 1000+ BF: 10-20% discount
• Full truck load: 20-30% discount

Negotiation Tips

• Buy during slow season (winter for most yards)
• Purchase multiple species together
• Accept lower grades for appropriate projects
• Build relationship with yard manager

Group Buying

Form buying co-op with other woodworkers. Split delivery costs and volume discounts.

Example:

• 5 woodworkers each need 200 BF walnut
• Individual price: $12/BF × 200 = $2,400 each
• Bulk order: 1,000 BF at $9.50/BF = $9,500 total
• Per person: $1,900 (saves $500 each)

How to Verify Lumber Yard Calculations

Step 1: Measure boards yourself

Bring a tape measure. Verify thickness, width, length.

Step 2: Calculate board feet independently

Use the formula for each board.

Step 3: Compare to yard's tally sheet

Check itemized invoice. Discrepancies happen.

Step 4: Understand rounding practices

Some yards round up to nearest 0.5 BF or whole number.

Common errors:

• Measuring width at widest point instead of narrowest
• Calculating nominal when actual dimensions differ significantly
• Including unusable defects in measurement

Moisture Content Considerations

Green Lumber (Fresh Cut)

• 30-80% moisture content
• Heaviest, most prone to warping
• Cheapest option
• Must dry 6-12 months before use

Air-Dried Lumber

• 12-20% moisture content
• Partially stable
• Moderate price
• May need further acclimation

Kiln-Dried (KD) Lumber

• 6-8% moisture content
• Most stable, ready to use
• Highest price (20-40% premium)
• Ideal for furniture and indoor projects

Shrinkage impact: Green 4/4 oak may shrink to 7/8" thick when dried. Buy extra if purchasing green lumber.

Rule of thumb: Add 15-25% to board foot calculation when buying green lumber for final dried project needs.

Adding Waste Factor

Real projects have waste—knots, splits, bad cuts, mistakes.

Common waste factors:

• 5-10% for straight cuts in clear lumber
• 10-20% for complex trim work
• 15-25% for lower grade lumber with defects
• 20-30% for intricate joinery or matching grain

Example with waste:

You need 80 board feet. Add 15%:

80 × 1.15 = 92 board feet to order

This saves emergency trips when you're one board short.

Board Foot vs Linear Foot vs Square Foot vs Cubic Foot

Board Foot (BF)

• Volume: 144 cubic inches
• Formula: (T × W × L) ÷ 12
• Use: Hardwood lumber pricing

Linear Foot (LF)

• Length only
• Formula: Length in feet
• Use: Trim, molding, pipe, rope

Square Foot (SF)

• Area: 144 square inches
• Formula: Length × Width
• Use: Flooring, roofing, tile

Cubic Foot (CF)

• Volume: 1,728 cubic inches
• Formula: L × W × H (all in feet)
• Use: Concrete, soil, gravel

Comparison table:

| Dimension | Board Foot | Linear Foot | Square Foot | Cubic Foot | |-----------|-----------|-------------|-------------|------------| | 2"×6"×10' | 10 BF | 10 LF | 5 SF | 0.83 CF | | 1"×12"×8' | 8 BF | 8 LF | 8 SF | 0.67 CF | | 1.5"×8"×12' | 12 BF | 12 LF | 8 SF | 1.0 CF |

Common Board Feet Mistakes

1. Using inches for length

The formula needs length in feet. Convert first: 96 inches ÷ 12 = 8 feet

2. Forgetting ÷ 12

Skip this and your number is 12× too big.

3. Mixing nominal and actual sizes

Using "1×6" as 1×6 when it's 0.75×5.5 overestimates volume.

4. Confusing with square feet

Square feet = area (length × width) Board feet = volume (thickness × width × length)

5. No waste factor

Even perfect math fails without accounting for defects.

6. Ignoring grade pricing

FAS walnut at $12/BF ≠ No. 2 walnut at $6/BF. Know what grade you're buying.

7. Not checking moisture content

Green lumber shrinks. Kiln-dried costs more but stays stable.

Quick Reference Calculations

Standard board dimensions:

| Size | Length | Board Feet | |------|--------|-----------| | 1×6 | 8' | 4.0 BF | | 1×6 | 10' | 5.0 BF | | 1×8 | 8' | 5.33 BF | | 1×12 | 8' | 8.0 BF | | 2×4 | 8' | 5.33 BF | | 2×6 | 10' | 10.0 BF | | 2×8 | 12' | 16.0 BF | | 2×10 | 14' | 23.33 BF |

Hardwood quarter-thickness conversion:

| Quarter | Rough Inches | Surfaced To | |---------|--------------|-------------| | 4/4 | 1.0" | 0.75" (3/4") | | 5/4 | 1.25" | 1.0" | | 6/4 | 1.5" | 1.25" | | 8/4 | 2.0" | 1.75" | | 10/4 | 2.5" | 2.25" | | 12/4 | 3.0" | 2.75" | | 16/4 | 4.0" | 3.75" |

Nominal vs Actual Size

Here's the catch: lumber labels lie.

A "1×6" board actually measures closer to 0.75 in × 5.5 in after milling.

Softwood nominal to actual:

| Nominal | Actual | |---------|--------| | 1×2 | 0.75" × 1.5" | | 1×4 | 0.75" × 3.5" | | 1×6 | 0.75" × 5.5" | | 1×8 | 0.75" × 7.25" | | 1×10 | 0.75" × 9.25" | | 1×12 | 0.75" × 11.25" | | 2×4 | 1.5" × 3.5" | | 2×6 | 1.5" × 5.5" | | 2×8 | 1.5" × 7.25" | | 2×10 | 1.5" × 9.25" | | 2×12 | 1.5" × 11.25" | | 4×4 | 3.5" × 3.5" |

Which size to use?

• Hardwood: Often sold by rough thickness (4/4, 5/4, 8/4) - calculate at rough dimension
• Softwood construction lumber: Sold by nominal, priced by nominal, calculate by nominal
• Your project plans: Use actual dimensions for accurate fit

When unsure, measure with a tape.

Why Hardwood Uses Board Feet

Hardwood comes in varying thicknesses and widths. Board feet standardizes volume so pricing stays consistent across all board sizes.

Without board feet system:

• 1"×12"×8' board would need different pricing than 1"×6"×16' board
• No standardized comparison possible
• Chaos in pricing

With board feet:

• Both boards = 8 BF
• Same price regardless of dimensions
• Simple, fair, consistent

Project Estimating

Table Top (48" × 72")

• Finished thickness: 1"
• Material: 5/4 stock (1" after surfacing)
• Area: 48" × 72" = 3,456 sq in = 24 sq ft
• Board feet needed: 24 BF
• With 15% waste: 24 × 1.15 = 28 BF

Bookshelf

• 6 shelves: 1" × 12" × 36" each
• BF per shelf: (1 × 12 × 3) ÷ 12 = 3 BF
• Total: 6 × 3 = 18 BF
• 2 sides: 1" × 12" × 60" each
• BF per side: (1 × 12 × 5) ÷ 12 = 5 BF
• Total sides: 2 × 5 = 10 BF
• Total project: 28 BF
• With 10% waste: 31 BF

Pro Tips

Quarter measurements: Hardwood thickness uses 4/4 (1 inch), 5/4 (1.25 inches), 8/4 (2 inches). Each quarter = 0.25 inch.

Bulk discounts: Buying 100+ board feet usually saves 5-10%. Ask about volume pricing.

Check moisture: Wet lumber shrinks as it dries. Kiln-dried (KD) is more stable and ready to use. Green lumber needs 6-12 months drying time.

Measure twice: Recalculate before finalizing orders. Mistakes cost money and project delays.

Grade appropriately: Don't buy FAS for rustic projects. Don't buy No. 2 Common for glass-top table bases. Match grade to visibility.

Inspect before buying: Look for checks, splits, excessive knots, sapwood, insect damage. Reject problem boards.

Buy extra length: Easier to cut down than stretch. Extra 1-2 feet per board provides flexibility for cutting around defects.

Acclimate lumber: Let wood adjust to shop humidity for 1-2 weeks before milling. Prevents warping after cutting.

Calculate by widest use: If project requires some 3/4" and some 1/2" pieces, buy all at 4/4 (1" rough) and mill to thickness. Don't try to buy multiple thicknesses.

Frequently Asked Questions

How do you calculate board feet? Use the formula: (Thickness in inches × Width in inches × Length in feet) ÷ 12. Example: A 2" × 8" × 10' board = (2 × 8 × 10) ÷ 12 = 13.33 board feet.

What is a board foot in lumber? One board foot equals 144 cubic inches of wood, or a piece measuring 1" thick × 12" wide × 12" long (1 foot). It's the standard volume measurement for pricing hardwood lumber.

How many board feet are in a 2×4×8? Using nominal dimensions: (2 × 4 × 8) ÷ 12 = 5.33 board feet. Most lumber yards price 2×4×8 softwood by the piece, not board feet.

Why divide by 12 in the board feet formula? Because thickness and width are measured in inches while length is in feet. Dividing by 12 converts everything to the same unit (board feet standard).

Is board feet the same as square feet? No. Square feet measure area (2 dimensions: length × width). Board feet measure volume (3 dimensions: thickness × width × length). A 1" thick board with 1 square foot of surface area = 1 board foot.

How much does a board foot of lumber cost? Depends on species and grade. Poplar costs $3-4/BF. Red oak costs $5-6/BF. Walnut costs $10-14/BF. Exotic species can exceed $20/BF. Prices vary by region and availability.

What does 4/4 mean in lumber? 4/4 (pronounced "four quarter") means 4 quarters of an inch, or 1 inch thick rough-sawn. After surfacing, 4/4 lumber typically measures 13/16" to 7/8" thick. 5/4 = 1.25", 8/4 = 2", etc.

Do lumber yards round up board feet? Practices vary. Some round to nearest 0.5 BF, others to whole numbers, some calculate precisely. Ask your yard's policy. Rounding up on many small boards can significantly increase costs.

Should I buy rough or surfaced lumber? Rough costs less but requires planing. Surfaced costs 10-20% more but saves workshop time. Buy rough if you have planer and need custom thicknesses. Buy surfaced (S2S or S4S) for convenience.

How do I convert linear feet to board feet? You need thickness and width. Formula: (Thickness × Width × Linear Feet) ÷ 12. Example: 10 linear feet of 1"×6" lumber = (1 × 6 × 10) ÷ 12 = 5 board feet.

Ready to calculate? Use our Percentage Calculator for instant results, or try our Unit Converter for all measurement conversions.