Board Feet vs Square Feet
Compare lumber volume with surface area and see why thickness matters.
Square feet omits thickness
Square feet measures face area. Board feet measures volume equivalent to square-foot area multiplied by thickness in inches. At one inch thick the numeric values match; at any other thickness they do not. That accidental one-inch match is why assumptions should always be written.
A 200 ft² surface at 0.5 inch contains 100 BF, while the same area at 1.5 inches contains 300 BF. Area alone cannot choose between those answers.
Coverage is not always net wood area
Cladding laps, flooring tongues, gaps, trimming and profile shapes can make purchased face area differ from visible coverage. The simple relationship assumes a uniform rectangular layer. Separate the geometric base from a waste or installation allowance.
Choosing the thickness basis
Use the thickness relevant to the decision: purchased rough thickness for an order comparison, measured finished thickness for installed solid volume, or a clearly stated nominal class when reviewing a nominal quotation. Do not mix thickness stages within one result.
Practical audit
Record area source, thickness and units. If the result is later priced per BF, retain the calculation before applying allowance. For mixed thicknesses, split the areas into separate calculations and add the resulting volumes.
Questions about this topic
When are square feet and BF equal?
For a uniform one-inch-thick layer.
Can I convert flooring coverage directly?
Only after choosing thickness and accounting separately for profile and waste.
What if thickness varies?
Calculate each thickness group separately.
Related BoardFoot Bench pages
Method and content reviewed 3 September 2026.