Square Feet to Board Feet Calculator
Convert covered area to board-foot volume by supplying thickness.
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Thickness turns area into volume
Square feet measures surface area; board feet measures volume. For a uniform layer, board feet equals square feet multiplied by thickness in inches. The thickness field is therefore mandatory. At one inch thick, one square foot equals one board foot; at three-quarter inch, each square foot equals 0.75 BF.
The relationship works for planning uniform panels or coverage only when the thickness describes the same material throughout. It does not account for tongue-and-groove profiles, bevels, gaps, waste or boards of mixed thickness.
Worked cladding example
Covering 160 ft² with material 0.75 inch thick contains 120 BF of geometric volume before waste: 160 × 0.75. Adding a 12% purchasing allowance is a separate decision, producing 134.4 BF in the price tool rather than changing the measured base volume.
Coverage and purchased stock differ
Visible face area may exclude laps, hidden tongues, trimming and defects. Finished thickness may also differ from the rough stock thickness used on a supplier tally. State which surface and which manufacturing stage the square-foot figure represents before converting it.
Validation checks
Both area and thickness must be finite and greater than zero. Use decimal inches consistently; 3/4 inch is 0.75, not 0.34. If thickness varies, calculate separate rows and add their board-foot volumes rather than using an unexplained average.
Questions about this topic
How many BF are 100 square feet at 1.5 inches?
150 BF before waste or machining allowances.
Can I omit thickness for 4/4 lumber?
No. Decide whether 4/4 is a nominal trade basis or enter the actual measured thickness.
Does the result include installation waste?
No. Add a separately labelled allowance after establishing base volume.
Related BoardFoot Bench pages
Method and content reviewed 3 September 2026.