Your lumber
Thickness and width are always in inches. Hardwood is sold by the board foot at its rough thickness, so use the quarter buttons. Softwood is often sold by the piece at a nominal size.
Price and waste
Fill in a board below to get the board feet.
A board foot is a measure of volume, not surface, so a thick board is more board feet than a thin one of the same face size. The yard charges for the rough size before planing, so enter what you are paying for, not the finished size.
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A 2 inch board costs twice what a 1 inch board does
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A board foot is how lumber is sold once you leave the big-box rack and buy from a real yard. It is a measure of volume, 144 cubic inches, so it counts thickness the same as face size. Put your cut list in above, by thickness, width, length and how many, and this adds up the board feet and what they cost, for the whole pile at once.
The math, in one line
Thickness in inches, times width in inches, times length in feet, divided by twelve. A board one inch thick, six inches wide and eight feet long is one times six times eight, over twelve, which is four board feet. Measure the length in inches instead and you divide by 144 rather than twelve. The calculator does both, and sums every row.
What the quarters mean
Hardwood thickness is written in quarters of an inch. 4/4 is an inch, 5/4 is an inch and a quarter, 6/4 is an inch and a half, 8/4 is two inches. Those are the rough sizes, before the board is planed flat and smooth, and the rough size is what the yard measures and charges for. So price the rough thickness, not the finished part you will cut from it. The buttons under the list fill it in for you.
Add for waste
Nobody uses a board end to end. You lose wood to checks and knots, to trimming and squaring up, and to matching grain across a panel. Ordering the exact finished amount leaves you short on the day. Fifteen to thirty percent over is normal, more when the parts are short or the grain has to match, and the waste box turns your finished total into the number to actually order.
Softwood is different
A 2x4 from the home center is sold by the piece at a nominal size that is already smaller than the name, so board feet rarely enter into it. Board feet are a hardwood and a rough-lumber thing. If you are pricing dimensional softwood, count pieces. If you are buying walnut or maple off a rack with a price per board foot chalked on it, this is the tool.
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