What is a board foot?

One square foot of material one inch thick: a volume unit. It is how foam, timber and most materials sold by bulk are priced, and it is the unit that makes different thicknesses comparable. Two hundred square feet of two-inch foam is 400 board feet; the same area in four-inch is 800. A price per square foot only means something if the thickness is stated alongside it.

Why does thickness matter acoustically?

A porous absorber works by making air move through it, and air movement is greatest a quarter of a wavelength from a hard surface. Foam thinner than about a quarter wavelength sits in the wrong place to do much. At 1 kHz a quarter wavelength is roughly three inches, at 250 Hz roughly thirteen, which is why one-inch foam is effective in the top octaves and nearly useless in the bottom ones. Each doubling of thickness buys about an octave.

Can I get low-frequency absorption without buying thick foam?

Often yes, by mounting thinner foam on standoffs with an air gap behind it. The gap moves the foam away from the wall and towards the quarter-wavelength position for lower frequencies, achieving a good part of what extra thickness would for the price of the standoffs. It is standard practice with fabric-wrapped panels and it is worth checking before buying four-inch foam, provided the depth is available.

Why is my cutting yield so poor on profiled foam?

Because the profile is cut away. A convoluted or wedge foam removes a substantial fraction of the blank by design, and that removed volume is not waste in any recoverable sense. Buying profiled product from a supplier who cuts it at scale is usually cheaper than cutting it yourself, and their quoted price already carries the loss. In which case set the yield here near 100% and use their per-board-foot price for the finished product.

Fibre is generally cheaper per unit of absorption and handles heat far better; foam is cleaner to handle, easier to profile, and does not need a facing to stop fibre release. Price them both. The fibre cost page works on density and thickness, and then decide on the non-price factors, because in most installations those decide it anyway.

Does the price include a facing?

Only if the quote does. Facings, fabric wraps, fire-rated coatings and adhesive backings all add to the per-board-foot price, sometimes substantially, and they change which product you are comparing against. When benchmarking two quotes, check the facing before concluding one supplier is expensive.

Acoustic, Noise, Vibration & NVH Products calculator

Acoustic Foam Cost Calculator (Board Feet)

Price an acoustic foam job the way foam is actually bought and actually works. Enter the area to treat, the thickness, the price per board foot, and the cutting yield. The calculator returns the total cost, the board feet to purchase, the delivered cost per square foot of treated surface, and a waste-loaded unit price you can compare against other quotes. Thickness is an input rather than an assumption buried in a per-square-foot rate, because thickness is what drives both the cost and the low-frequency absorption, and a quote that hides it is not comparable to one that does not.

What this calculator does

Price an acoustic foam job on the basis foam is actually sold and actually works: volume in board feet, with thickness visible rather than buried in a per-square-foot rate.
Use it for comparing foam quotes given at different thicknesses or in different units, costing the step from two-inch to four-inch foam for a low-frequency requirement, deciding whether to buy pre-cut profiled foam or cut it in house, building the material line of an acoustic treatment quote, checking whether a cutting yield problem is worth solving.
Price an acoustic foam job on the basis foam is actually sold and actually works: volume in board feet, with thickness visible rather than buried in a per-square-foot rate.

Formula used

Net board feet = area × thickness in inches (one board foot = 1 ft² at 1 in)
Board feet to buy = net board feet ÷ cutting yield
Total foam cost = board feet to buy × price per board foot
Delivered cost per ft² = total foam cost ÷ area treated
Cost of cutting waste = total cost − net board feet × price
Waste-loaded price per board foot = price ÷ cutting yield

Inputs explained

Area to treat: Surface area the foam covers, before any cutting allowance.
Foam thickness: Nominal thickness. This drives both cost and low-frequency absorption, which is why it belongs on the page rather than inside a per-square-foot price.
Foam price per board foot: Price for one square foot at one inch thick. If the supplier quotes per square foot at a stated thickness, divide by that thickness in inches.
Cutting yield: Percentage of purchased foam that ends up installed. Straight rectangular cuts run above 95%; contoured or wedge profiles considerably less.

How to use the result

Best suited to comparing foam quotes given at different thicknesses or in different units, costing the step from two-inch to four-inch foam for a low-frequency requirement, deciding whether to buy pre-cut profiled foam or cut it in house, building the material line of an acoustic treatment quote, checking whether a cutting yield problem is worth solving.
Prices material only. Adhesive, fixings, labor, freight and cutting charges are separate, and for a thin foam job they can exceed the foam itself. Predicts no acoustic performance. It does not know the foam's absorption coefficients, only what its volume costs. Ignores minimum order quantities and bun sizes, which on small jobs can dominate the calculation entirely. Assumes cost is linear in thickness, which holds for foam sold by volume but not for stock thicknesses priced as separate products. Does not compare foam against fibre; the fibre cost page prices that alternative on its own terms.

Common questions

What is a board foot? One square foot of material one inch thick: a volume unit. It is how foam, timber and most materials sold by bulk are priced, and it is the unit that makes different thicknesses comparable. Two hundred square feet of two-inch foam is 400 board feet; the same area in four-inch is 800. A price per square foot only means something if the thickness is stated alongside it.
Why does thickness matter acoustically? A porous absorber works by making air move through it, and air movement is greatest a quarter of a wavelength from a hard surface. Foam thinner than about a quarter wavelength sits in the wrong place to do much. At 1 kHz a quarter wavelength is roughly three inches, at 250 Hz roughly thirteen, which is why one-inch foam is effective in the top octaves and nearly useless in the bottom ones. Each doubling of thickness buys about an octave.
Can I get low-frequency absorption without buying thick foam? Often yes, by mounting thinner foam on standoffs with an air gap behind it. The gap moves the foam away from the wall and towards the quarter-wavelength position for lower frequencies, achieving a good part of what extra thickness would for the price of the standoffs. It is standard practice with fabric-wrapped panels and it is worth checking before buying four-inch foam, provided the depth is available.
Why is my cutting yield so poor on profiled foam? Because the profile is cut away. A convoluted or wedge foam removes a substantial fraction of the blank by design, and that removed volume is not waste in any recoverable sense. Buying profiled product from a supplier who cuts it at scale is usually cheaper than cutting it yourself, and their quoted price already carries the loss. In which case set the yield here near 100% and use their per-board-foot price for the finished product.
Foam or fibre? Fibre is generally cheaper per unit of absorption and handles heat far better; foam is cleaner to handle, easier to profile, and does not need a facing to stop fibre release. Price them both. The fibre cost page works on density and thickness, and then decide on the non-price factors, because in most installations those decide it anyway.

Last reviewed 2026-08-25.