Thickness or density, which should I buy?

Thickness, almost always. Double either one and the bill doubles, but thickness moves useful absorption about an octave lower while density buys a smaller gain and then stops. Density earns its place for rigidity, fire rating or airflow erosion resistance.

Why does absorption stop improving above about 8 pcf?

A porous absorber works by letting air move through it and dissipating that motion. Flow resistivity has an optimum: too low passes sound through, too high reflects it off the face. Denser fiber pushes past the optimum.

How do I convert a per-batt price?

Work out the batt's weight and divide. A 24 by 48 inch batt at 3 inches thick is 2 cubic feet, so at 3 pcf it weighs 6 pounds. A $7 batt is therefore about $1.17 per pound.

Does compressing the batt change anything?

Yes, in both directions. Compression raises installed density and flow resistivity but reduces thickness, which is the larger loss. Squeezing a 4-inch batt into a 3-inch cavity also means you paid for four inches.

Acoustic, Noise, Vibration & NVH Products calculator

Acoustic Fiber Cost Calculator (Density and Thickness)

Price mineral wool or glass fiber the way it is sold, by weight. Enter area, batt thickness, density and price per pound; the page returns total cost, weight and a thickness-normalised unit cost.

What this calculator does

Price mineral wool or glass fiber by weight, so the cost of density and the cost of thickness are separately visible.

Formula used

Volume = area × thickness in inches ÷ 12
Fiber weight = volume × density
Total fiber cost = fiber weight × price per pound
Cost per ft² = total cost ÷ area; areal density = density × thickness ÷ 12
Cost per ft² per inch = total cost ÷ (area × thickness)

Inputs explained

Area to Treat: Surface area the fiber covers.
Batt Thickness: Installed thickness, the strongest lever on low-frequency absorption.
Fiber Density: Nominal density; acoustic mineral wool commonly runs 3 to 8 pcf.
Fiber Price per Pound: Delivered price per pound, including any facing or scrim.

How to use the result

Best suited to choosing thicker low-density batts or denser thin ones, converting a per-batt price into a per-pound rate, checking dead load a hung fiber treatment adds.
Prices material only: no facing labor, framing, retaining mesh, fixings or freight. Predicts no absorption; performance also depends on fiber diameter and binder, which are not inputs. Ignores batt sizes and minimum order quantities, which matter on small jobs.

Common questions

Thickness or density, which should I buy? Thickness, almost always. Double either one and the bill doubles, but thickness moves useful absorption about an octave lower while density buys a smaller gain and then stops. Density earns its place for rigidity, fire rating or airflow erosion resistance.
Why does absorption stop improving above about 8 pcf? A porous absorber works by letting air move through it and dissipating that motion. Flow resistivity has an optimum: too low passes sound through, too high reflects it off the face. Denser fiber pushes past the optimum.
How do I convert a per-batt price? Work out the batt's weight and divide. A 24 by 48 inch batt at 3 inches thick is 2 cubic feet, so at 3 pcf it weighs 6 pounds. A $7 batt is therefore about $1.17 per pound.
Does compressing the batt change anything? Yes, in both directions. Compression raises installed density and flow resistivity but reduces thickness, which is the larger loss. Squeezing a 4-inch batt into a 3-inch cavity also means you paid for four inches.

Last reviewed 2026-10-01.