People ask for spray foam's cost 'per square foot,' but that number is almost meaningless on its own, because price tracks board feet - a square foot at one inch thick. A square foot sprayed to 6 inches costs six times a square foot sprayed to one. Same 'square foot,' very different job.
Square foot vs board foot
- Square foot = area only.
- Board foot = area x thickness. It's the unit installers actually price in, because it captures how much foam is used.
Why the distinction protects you
A contractor quoting a flat per-square-foot rate is hiding the thickness assumption - and thickness is most of the cost. Ask for the board-foot basis and you can compare quotes honestly.
Convert your job
The calculator turns your area and target thickness into an estimated board-foot quantity - a real planning number. Then get a quote. See the full cost guide.