Board Foot Calculator: Lumber Volume & Cost
Hardwood lumber is priced by the board foot, and board-foot math confuses everyone the first time — a 2 × 4 is not 8 board feet, and a "six-quarter" board is not 6 inches thick. This free board foot calculator takes the guesswork out: enter each board's thickness, width, length and quantity, add as many different sizes as your order includes, and it totals the board feet and the price at your lumberyard's rate.
Lumber Board Foot Calculator
How to Use This Board Foot Calculator
Enter each board size in your order: thickness and width in inches, length in feet, and how many of that exact size you are buying. Need multiple sizes? Click "Add another board size" and enter the next one — the tool adds everything together.
Use nominal dimensions for construction lumber (a 2 × 4, even though it measures 1.5 × 3.5) and actual measured dimensions for hardwood. If your lumberyard quotes a price per board foot — $6 for cherry, $12 for walnut, more for exotics — enter it to see the total cost of the order. Then click Calculate.
The Board Foot Calculation Formula
One board foot is a volume of 144 cubic inches — think of a board 1 inch thick, 12 inches wide and 12 inches long. The formula for any piece is board feet = (thickness × width × length) ÷ 12, with thickness and width in inches and length in feet. Multiply by quantity and sum all the sizes in your order.
Worked example: a 2 × 4 × 8 is (2 × 4 × 8) ÷ 12 = 5.33 board feet. Four of them: 5.33 × 4 = 21.33 board feet. At $6 per board foot, that order costs 21.33 × 6 = $128.00. Notice the length is in feet while thickness and width are in inches — mixing them up is the most common board-foot mistake.
Pro Tips for Buying Lumber by the Board Foot
Hardwood is priced by the board foot, and rough-sawn boards are sold in quarters: 4/4 is 1 inch thick, 6/4 is 1.5 inches, 8/4 is 2 inches. The yard usually calculates from rough thickness, so surfacing the board costs you a little volume — plan your project on the finished dimensions and add about 20% for waste.
Construction lumber is different: it is sold per piece at standard sizes, and the "2 × 4" label is nominal — the actual board is 1.5 × 3.5 inches. When you price a project with this calculator, use nominal sizes for framing lumber and real measurements for hardwood boards you select yourself.
Frequently Asked Questions
How do I calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12: (T × W × L) ÷ 12. A board foot is a volume of 144 cubic inches — a 1-inch-thick board, 12 inches wide and 12 inches long.
How many board feet is a 2x4x8?
A 2x4x8 is (2 × 4 × 8) ÷ 12 = 5.33 board feet. Four of them make 21.33 board feet.
What is the difference between board feet and linear feet?
A linear foot is a length measurement — any board 1 foot long is 1 linear foot, whatever its size. A board foot is a volume measurement: 144 cubic inches of wood. A 1x12x1 and a 2x6x1 are each 1 board foot, but both are 1 linear foot.
Why is hardwood priced by the board foot?
Hardwood boards come in random widths and lengths from the sawmill, so selling by the board foot (volume) is the only fair way to price them. Softwood construction lumber, cut to standard sizes, is sold per piece instead.