Almighty Calculator

Board Foot Calculator

Board feet = thickness (in) × width (in) × length (ft) ÷ 12, multiplied by the number of pieces.

in
in
ft
Optional. Set to 0 to ignore cost.
Total board feet
40BF
Board feet per piece4 BF
Total cost180 $

Board feet are figured from nominal or rough dimensions as sold. Use the thickness the mill or seller charges by (e.g. 4/4 = 1 inch).

Show the math

BF per piece = 1 × 6 × 8 ÷ 12 = 4
Total BF = 4 × 10 pieces = 40 BF
Cost = 40 BF × $4.5 = $180

Rounded the same way as the result above.

How it works

A board foot is a volume of wood equal to a piece 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches). Hardwood lumber is priced and sold by the board foot, so knowing the count lets you compare quotes and plan a project.

Enter the thickness and width in inches and the length in feet. The calculator multiplies them, divides by 12, then multiplies by the number of pieces. If you enter a price it also gives the total cost.

BF = (thickness in × width in × length ft) ÷ 12 × pieces Metric: BF = (mm × mm × m) ÷ (25.4 × 25.4 × 0.3048 × 12)

Worked example

Ten 1-inch-thick, 6-inch-wide, 8-foot-long red oak boards at $4.50 per board foot:

  1. BF per piece = 1 × 6 × 8 ÷ 12 = 4
  2. Total BF = 4 × 10 pieces = 40 BF
  3. Cost = 40 BF × $4.5 = $180
InputValue
Thickness1 in
Width6 in
Length8 ft
Number of pieces10
Price per board foot ($)4.5
ResultValue
Total board feet40 BF
Board feet per piece4 BF
Total cost180 $

Assumptions and limits

  • Uses the dimensions you enter. Rough-sawn lumber is usually measured before planing; surfaced (S4S) lumber is often still sold on the rough thickness.
  • Thickness is normally measured in quarters: 4/4 = 1", 5/4 = 1.25", 8/4 = 2".
  • Does not account for waste. Add 15–25% for defects and milling loss when buying for a project.

Common questions

How many board feet are in a 2x4?

A 2x4 that is actually 1.5" × 3.5" is 1.5 × 3.5 × 8 ÷ 12 = 3.5 BF for an 8-foot stick. Using the nominal 2" × 4" size gives 5.33 BF. Softwood dimensional lumber is usually sold by the piece or linear foot, not by the board foot.

How do I calculate board feet for boards of different sizes?

Calculate each size separately with this tool and add the results. The formula works per piece, so mixed stacks are just a sum.

What does 4/4 mean?

4/4 (four-quarter) means the rough lumber is 1 inch thick. 5/4 is 1.25 inches, 6/4 is 1.5 inches, and 8/4 is 2 inches.

How much extra should I buy?

Plan on 15–25% extra for knots, checks, end trim, and milling. Highly figured or wide-panel work can need more.

Sources

  • Standard definition of the board foot: 144 cubic inches of wood (1 in × 12 in × 12 in). The calculation is arithmetic.

Updated 2026-09-30