Board Foot To Linear Foot Conversion

Board feet and linear feet answer two different questions about the same stack of lumber — board feet measures volume, linear feet measures length — and the two only convert into each other once you fix a width and a thickness, which is the step people skip when a lumberyard quote in board feet doesn't match a cut list written in linear feet.

The conversion, worked from the formula

Board feet is defined as (thickness in inches x width in inches x length in feet) / 12. Rearranged to solve for length instead of board feet: linear feet = (board feet x 12) / (thickness in inches x width in inches). The width and thickness have to be known and fixed for this to mean anything — "100 board feet" alone doesn't convert to a linear-foot figure until you say what size stock it's in, because 100 board feet of skinny 1x4 is a very different length of material than 100 board feet of a wide 2x10.

A worked example

Take 100 board feet of actual 1.5" x 3.5" stock (a 2x4, in its real dimension): linear feet = (100 x 12) / (1.5 x 3.5) = 228.6 linear feet. Check this directly against the board foot calculator, which will confirm that 228.6 linear feet of 1.5" x 3.5" stock comes back out to 100 board feet. For the equivalent conversion worked on 2x6 stock specifically, see /answers/how-many-linear-feet-in-100-board-feet-of-2x6/ — a single-number instance of the same method, not a repeat of it.

Why the same board-foot figure means very different lengths at different sizes

The relationship is inverse to the cross-sectional area, not to any single dimension — doubling a board's width halves the linear footage you get from the same board-foot total, and halving the thickness doubles it. This is why a lumberyard quoting "500 board feet of walnut" for a project is not yet a usable number for a cut list until you know what dimension that walnut is being sold in; the same 500 board feet could be a short stack of thick 8/4 slabs or a much longer run of thin 4/4 boards.

Where this conversion actually gets used

Cut-list planning is the most common real use: a project's material list is naturally expressed in linear feet per specific board size (need 40 linear feet of 1x4 for face frames, 18 linear feet of 6/4 for legs), while a supplier often prices and quotes in board feet regardless of what specific stock dimension you're pulling from. Converting the quote back to linear feet per size, using the formula above for each distinct dimension in the order, is what turns a single board-foot total into an actual shopping list — and it's also the check worth running in reverse, converting a linear-foot cut list back to board feet, before placing an order, to make sure the total matches what the supplier is charging for.

A caveat worth stating plainly

This conversion uses the actual dimension, not the nominal one — running it against a nominal "2 inch by 4 inch" figure instead of the real 1.5" x 3.5" will produce a linear-foot number that doesn't match what you actually receive. See /reference/nominal-vs-actual-2x4/ for the actual-size figures across the whole dimensional-lumber range if you're converting for a size other than the worked example above, and /reference/board-foot-to-square-foot-conversion/ for the related but distinct conversion used for coverage-area material like decking and flooring rather than length-based cut lists.

Mixed cut lists need the conversion run per size, not once

A real project cut list rarely uses one board dimension throughout — a table might need 6/4 legs, 4/4 aprons, and 4/4 top boards in three different widths. Each of those is a separate thickness-and-width pair, so each needs its own linear-feet-per-board-foot conversion; there's no single blended figure that covers a mixed order, because the formula's denominator changes with every dimension. The practical workflow is to total board feet needed per distinct size first, then convert each total to linear feet separately, rather than trying to convert one grand total and split it across sizes afterward — the second approach silently assumes every size uses lumber at the same rate per board foot, which is exactly the assumption this page exists to correct.

Rounding and waste

The raw conversion assumes zero waste — every inch of length purchased ends up in the finished project. Real cut lists never achieve that, because crosscuts lose material to saw kerf and boards get culled for defects, so add a waste allowance on top of the raw converted linear footage before ordering; /reference/lumber-yield-and-waste-factor-guide/ covers what allowance is reasonable for a given material and project type, a separate consideration from the pure unit conversion this page covers.