Board Foot Calculator
Calculate the volumetric board footage (BF / FBM), linear feet, and total cost of hardwood and softwood lumber based on thickness, width, length, and quantity.
Calculation Results
Volumetric board footage of the lumber tally (1 BF = 144 cubic inches).
Total combined length of all boards running end to end.
Total purchase price based on hardwood supplier per-board-foot pricing.
How This Calculator Works
Calculate your lumber purchase order in seconds:
- Select Thickness: Choose standard hardwood quarter scales (4/4, 5/4, 8/4) or enter nominal thickness directly.
- Enter Board Dimensions: Input width in inches, board length in feet, and total piece quantity.
- Add $/BF Rate: Enter the sawmill price per board foot (e.g. $4.50/BF for red oak or $9.00/BF for walnut).
- Review Output: Instantly view total board feet (FBM), linear feet, and total invoice cost.
Formula & Calculations
A board foot (FBM - Foot Board Measure) is the standard commercial unit of volume for rough and surfaced lumber in North America:
1. Volumetric Board Foot Formula
One board foot equals 144 cubic inches (the volume of a 1" thick × 12" wide × 12" long board):
Board Feet = [Thickness (in) × Width (in) × Length (in) × Quantity] / 144
When length is expressed in feet, the formula simplifies to:
Board Feet = [Thickness (in) × Width (in) × Length (ft) × Quantity] / 12
2. Hardwood Quarter-Thickness Scale
Hardwood sawmills measure thickness in quarters of an inch (rough-sawn dimensions before final planing):
- 4/4 (Four-Quarter): 1.0 inch rough thickness (yields 3/4" S2S surfaced lumber).
- 5/4 (Five-Quarter): 1.25 inches rough thickness (yields 1" S2S lumber).
- 6/4 (Six-Quarter): 1.5 inches rough thickness (yields 1-1/4" S2S lumber).
- 8/4 (Eight-Quarter): 2.0 inches rough thickness (yields 1-3/4" S2S lumber).
3. Nominal vs. Actual Sizing
Softwood framing lumber (2x4, 2x6) uses nominal sizes for board foot math: a 2x4 is calculated at 2" × 4", even though its planed size is 1.5" × 3.5".
Step-by-Step Calculation Examples
Hardwood Tabletop Build (Six 8/4 Walnut Boards x 8ft x 6in)
Calculating board feet and invoice cost for rough 8/4 black walnut at $10.50/BF.
- thickness_type: 8/4
- thickness: 2
- width: 6
- length: 8
- quantity: 6
- cost_per_bf: 10.5
- board_feet: 48
- total_linear_feet: 48.0 ft
- total_cost: $504.00
Frequently Asked Questions
What is a board foot?
A board foot is a specialized unit of volumetric measurement used in the lumber and timber industries. One board foot represents a volume of 144 cubic inches, equivalent to a board 12 inches wide, 12 inches long, and 1 inch thick.
What is the difference between board feet and linear feet?
Linear feet (or running feet) measures only the continuous length of a board regardless of its width or thickness. Board feet measures total 3-dimensional wood volume. A 10-foot long 2x4 has 10 linear feet, but contains 6.67 board feet.
What does "4/4" or "8/4" lumber mean?
Sawmills measure hardwood lumber thickness in increments of 1/4 inch. 4/4 (four-quarter) is 1 inch thick; 5/4 is 1.25 inches thick; 6/4 is 1.5 inches thick; and 8/4 is 2 inches thick in its rough, un-planed state.
Do you calculate board feet using nominal or actual dimensions?
Lumber suppliers calculate board footage using nominal (rough-sawn) dimensions. When you buy surfaced (planed) 2x4s or 4/4 hardwood, you pay for the original rough lumber volume before the sawmill planed off wood shavings.
How many board feet are in a 2x4x8?
A standard 2x4 stud measuring 8 feet long contains exactly 5.33 board feet: (2 inches × 4 inches × 8 feet) / 12 = 5.33 BF.
How do you calculate the board footage of a standing tree or log?
Log scaling rules (such as the Doyle Log Rule, Scribner Decimal C Rule, or International 1/4-inch Rule) use mathematical formulas based on the small-end log diameter inside the bark and log length to estimate the board feet of sawn lumber a log will yield.