The Formula Behind This Calculator
Board feet per board = thickness (in) x width (in) x length (ft) / 12
Total board feet = board feet per board x quantity
Total cost = total board feet x price per board foot
The formula is a volume in disguise: thickness times width times length in inches gives cubic inches, and dividing by 144 would give cubic feet. The lumber trade divides by 12 instead because the length enters in feet, and the quotient is the board foot, defined as 144 cubic inches. Once you see one board foot as a chunk of wood 1 inch thick and a foot square, the formula never needs memorizing again: any board is some number of those chunks.
Worked Example: Ten 2 by 6 Boards, 8 Feet Long
A workbench build calls for ten boards of 2 by 6 construction lumber, 8 feet long, priced against a $5 per board foot reference.
- Per board: 2 x 6 x 8 / 12 = 8 board feet.
- Total: 8 x 10 = 80 board feet.
- Cost at $5: 80 x $5 = $400.
- With a 20 percent allowance: 96 board feet, $480 worth of stock.
Run the same dimensions at a home center mentally and you will notice construction lumber sells per piece, often $10 to $16 for that board, which works out near $1.25 to $2 per board foot: softwood framing lumber is priced by logistics, hardwood by volume. The calculator serves both worlds, because the tally is how you compare a per piece tag against a per board foot quote and discover which yard is actually cheaper for your cut list.
A Complete Guide to Board Feet and Lumber Buying
Board foot pricing intimidates new woodworkers and quietly taxes experienced ones who never learned to tally in their head. It exists because hardwood is a natural, variable product: boards arrive in random widths, and charging by the piece would make a 10 inch wide board the same price as a 5 inch board of the same length. Volume pricing fixes that. This guide covers the tally, the grading and thickness language of hardwood yards, and how to leave with the wood your project actually needs.
Quarters, Surfacing and What Thickness Means
Hardwood thickness is spoken in quarters of an inch as rough sawn: 4/4 is one inch, 5/4 is one and a quarter, 8/4 is two inches. After surfacing two sides (the S2S you see on price lists), 4/4 stock finishes near 13/16 inch, and yards sell it surfaced for a small premium or rough for you to mill. Your project plan must start from finished thickness and work back: a tabletop that must finish at 3/4 inch comes from 4/4 stock milled carefully, and a leg that finishes at 1.75 inches needs 8/4. Buying rough and milling it yourself saves money and teaches you the wood; buying S2S saves a weekend and a planer knife set. Both are legitimate.
Grades in Plain Language
The top hardwood grade, FAS, promises large clear cuttings and prices accordingly. Selects and #1 Common step down in the size of clear pieces you can expect, at meaningfully lower prices per board foot. For furniture with modest part sizes, #1 Common is the value play of the yard: its defects dodge most parts, and the tally you pay for only hurts if your cut list needs long clear boards. Shorts bins, discounted boards under 4 feet, are the hidden economy section for small projects, boxes, cutting boards and tool handles. Match the grade to the largest clear part in your plan, not to your aspirations for the woodpile.
Estimating a Project From a Cut List
The professional method is unglamorous and exact. List every finished part with its dimensions, convert each to board feet at rough thickness, sum them, then add your waste factor: 10 percent for straight construction work, 20 to 25 percent for furniture in figured or character stock, 30 percent if this is your first project in a species that hides defects inside the board. Buy the tally in boards whose widths suit your widest parts, sighting down each board for crook before it goes on the cart. A board can be tallied correctly and still be the wrong board; the calculator adds the numbers, your eyes approve the lumber.
Storing What You Bought
Lumber keeps moving until it acclimates to your shop. Stack it flat, stickered with thin strips between layers so air reaches every face, out of direct sun, for at least a few days before milling, a week or more for thick stock brought in from a cold yard. Ends lose moisture fastest and check first; the yard's end sealer is worth leaving on until final cuts. These habits are why the extra 20 percent exists: wood that checks, cups or reveals a knot exactly at your mortise is replaced from the surplus, not from a second trip and a new dye lot of grain. For the framing side of lumber math, our Stud Wall Framing Calculator counts boards by the piece for wall building.
Moisture: The Number Behind Half of Lumber Trouble
Furniture lumber should arrive at 6 to 9 percent moisture content, kiln dried, and construction lumber is typically stamped KD at 19 percent or below. A ten dollar pin meter pays for itself at the yard: boards much above 10 percent for furniture work will shrink, warp and open joints after they join your heated house. Air dried stock is cheaper per board foot and wonderful for outdoor projects, but in most climates it equilibrates around 12 to 14 percent, fine for a workbench or fence, risky for a dining table until it spends time stickered indoors. If a dealer's price for kiln dried walnut looks too good, put the meter in the board before you put the board in your truck. The tally from this calculator tells you what the wood costs; the moisture reading tells you whether it was a bargain.