How Many Board Feet Calculator
Enter a board’s thickness and width in inches and its length in feet, and this calculator applies the standard hardwood-lumber formula — (thickness x width x length) / 12 — to give you the board feet, a number of boards multiplier, and an estimated total cost.
Quick Answer
Enter a board’s thickness and width in inches and its length in feet, and this calculator applies the standard hardwood-lumber formula — (thickness x width x length) / 12 — to give you the board feet, a number of boards multiplier, and an estimated total cost.
How Many Board Feet Calculator
Enter your values below for an instant result, then see the formula, worked example, and common mistakes.
Enter your lumber dimensions and click calculate.
How to Use This Calculator
Hardwood is typically sold using the “quarter” system — 4/4 means 1 in thick, 5/4 means 1.25 in, 8/4 means 2 in, and so on, referring to rough-sawn (not surfaced) thickness.
Measure the actual width of the board, or use the width you plan to buy/cut to.
Board foot convention uses length in feet while thickness and width are in inches — this is the one dimension that is NOT in inches in the standard formula.
The calculator multiplies the per-board board-foot figure by quantity to get your total order size.
Hardwood lumber yards price by the board foot, and rates vary widely by species — get a current quote before finalizing your budget.
Formula
Board feet = (Thickness in inches x Width in inches x Length in feet) / 12. This is the standard formula used throughout the U.S. hardwood lumber industry — note that length is the one dimension expressed in feet, not inches, in this version of the formula.
One board foot equals 144 cubic inches of wood — the volume of a board 1 in thick, 12 in wide, and 12 in (1 ft) long.
Reference Table: The Lumber “Quarter” Thickness System
| Quarter designation | Rough thickness | Typical surfaced (S4S) thickness |
|---|---|---|
| 4/4 | 1 in | ~13/16 in (0.81 in) |
| 5/4 | 1.25 in | ~1-1/16 in (1.06 in) |
| 6/4 | 1.5 in | ~1-5/16 in (1.31 in) |
| 8/4 | 2 in | ~1-3/4 in (1.75 in) |
Common Mistakes to Avoid
- Entering width in feet instead of inches — the standard board-foot formula uses width in INCHES, not feet; only length uses feet. Mixing this up produces a wildly wrong result.
- Using nominal quarter-thickness (e.g. 4/4 = 1 in) when the board has already been surfaced (planed) thinner — if you need the actual finished-thickness volume, use the true surfaced thickness, not the nominal rough-sawn figure.
- Forgetting to multiply by quantity when pricing an order of multiple boards.
- Assuming board feet and square feet are the same measurement — board feet is a volume measurement that factors in thickness, while square feet is a flat area measurement that does not.
When the Estimate May Be Wrong
This calculator gives the mathematically exact board-foot figure for the dimensions entered. It does not add any waste, defect, or kerf-loss allowance — add 10-15% when actually ordering lumber for a project to account for cutting losses and material with defects.
FAQs
What is the correct formula for board feet?
Board feet = (thickness in inches x width in inches x length in feet) / 12. Length is the one dimension expressed in feet rather than inches in this standard version of the formula.
What does 4/4 mean in lumber terms?
4/4 (read as “four quarter”) means 1 in of rough-sawn thickness, using the traditional quarter-inch lumber grading system where 4/4 = four quarter-inches = 1 in.
Is board feet the same as square feet?
No — board feet is a volume measurement (it includes thickness), while square feet measures only flat area. A thicker board has more board feet than a thinner board of the same length and width.
How many board feet are in a standard 2×4?
An 8 ft long 2×4, using actual dimensions of 1.5 in x 3.5 in, is 1.5 x 3.5 x 8 / 12 = 3.5 board feet.
Sources and Methodology
Board foot formula and the hardwood “quarter” thickness system sourced from the Hardwood Manufacturers Association and Woodworkers Source published board-foot and lumber-grading guidance.
