Board Ft Calculator
Calculate board feet from lumber dimensions, compare Doyle/Scribner/International 1/4 log scales, or convert square feet to board feet by thickness.
Calculate board feet for dimensional lumber, estimate log board-foot scale under Doyle, Scribner and International 1/4-inch rules, or convert square feet to board feet by thickness.
Board feet result
Board Ft Calculator
This board ft calculator handles three related jobs without mixing them together: board measure for sawn lumber, log-scale estimates for round logs, and square-feet-to-board-feet conversion when material thickness is known.
NIST defines one board foot as the volume of a board 1 foot long, 1 foot wide and 1 inch thick, equal to 144 cubic inches.
Board Foot Formula for Lumber
For rectangular lumber measured in inches and feet:
Board feet = thickness (in) × width (in) × length (ft) ÷ 12 × quantity
Example: ten boards measuring 1 inch × 6 inches × 8 feet contain 40 board feet. If hardwood is priced per board foot, enter the price to estimate material cost.
For rough hardwood sold as 4/4, 5/4, 6/4 or 8/4, use the thickness basis used by the seller rather than automatically substituting the final surfaced thickness.
Board Ft Calculator for Logs
A board ft calculator log estimate is different from measuring already-sawn lumber. A round log contains bark, slabs, taper, kerf and defects, so foresters and mills use log rules to estimate sawn-lumber yield from the small-end diameter inside bark and log length.
Penn State and Virginia Tech identify Doyle, Scribner and International 1/4-inch as common North American rules and emphasize that they can produce materially different volumes for the same log. International 1/4 is generally a closer predictor of saw yield, while Doyle can strongly underscale small logs.
Doyle rule
BF = (D − 4)² × L ÷ 16, where D is small-end diameter inside bark in inches and L is log length in feet.
Scribner rule
Scribner is fundamentally a diagram/table rule rather than one exact universal equation. This calculator reports the common approximation (0.79D² − 2D − 4) × L ÷ 16 and labels it as an estimate. For a commercial scale ticket, use the official table/procedure required by the transaction.
International 1/4-inch rule
The International 1/4-inch result uses the length-and-diameter equation that reproduces common published International 1/4 tables closely across normal saw-log sizes. It incorporates the rule’s 1/4-inch kerf and taper assumptions rather than treating a log as a solid cylinder.
Sq Ft to Board Ft Calculator
Square feet measure area while board feet measure volume, so thickness is required. Because one board foot is exactly one square foot at one inch thick:
Board feet = square feet × thickness in inches
For example, 100 square feet of 2-inch-thick material equals 200 board feet. A square-foot value by itself cannot be converted to board feet without a thickness assumption.
Board Feet vs. the Existing Lumber Calculator
SeriesCalculator’s Lumber Calculator is designed for project ordering and also estimates linear feet, quantity with waste, physical weight and cost. This Board Ft Calculator is narrower and faster when your main task is board measure, log scaling, or square-feet-to-board-feet conversion.
Frequently Asked Questions
How many cubic feet are in one board foot?
One board foot is 144 cubic inches, which is 1/12 of a cubic foot.
Do I use actual or nominal lumber dimensions?
Use the dimensions appropriate to the way the lumber is being sold or tallied. Board-foot pricing for rough hardwood commonly uses stated rough thickness, while physical weight/finished dimensions are a different question.
Why do Doyle, Scribner and International give different log totals?
They make different assumptions about how boards can be recovered from a round, tapered log and about saw kerf and waste. The scale rule is part of the commercial measurement convention, not a change in the log’s physical wood volume.
Can I convert square feet to board feet without thickness?
No. Square feet are area and board feet are volume. You must know or assume the material thickness in inches.
Methodology and Sources
The board-foot definition is cross-checked against NIST Handbook 130. Log-rule behavior and comparisons are cross-checked against Penn State Extension, Virginia Cooperative Extension and University of Florida IFAS forestry references. The log mode is an estimating aid; transactions should use the scaling rule, rounding convention and defect deductions specified by the buyer, mill, agency or contract.