Sound & acoustic insulation calculator
Filling an interior wall with batt quiets it down — and this counts the bundles. Give it the wall area and the coverage printed on the bag and it rounds up to whole bundles. It is a quantity tool, not an acoustic rating.
Calculator
200 ft² of interior wall takes about 3 bundles of safb/mineral-wool batt. Insulation is one part of an STC assembly — this is QUANTITY only, not an acoustic-engineering rating (mass, decoupling and sealing also matter; see the data sheet).
Formula
bundles = ceil(interior_wall_area ÷ coverage_per_bundle)
One wall face, since sound batt fills the stud cavity like thermal batt. Round up: a partial bundle still means buying a whole one, and you want the cavities full, not scrimped.
Worked example
A 200 ft² interior wall with 88 ft²/bundle batt is 200 ÷ 88 = 2.27, rounded up to 3 bundles. Use a batt that fills the cavity depth — a friction-fit, full-depth batt does far more for sound than a thin one that leaves an air gap, even though the bundle count is the same.
Insulation is one part of a quiet wall
This tool sizes the batt, but a genuinely quiet wall is a whole assembly. Do not expect insulation alone to do it:
- Fill, do not stuff. Batt damps sound by filling the cavity, not by packing it tight. A full-depth, friction-fit batt with no gaps is the goal; over-compressing it helps neither sound nor R.
- Mineral wool is the acoustic pick. Denser mineral-wool / safb batts outperform light fiberglass for sound — but coverage per bundle is what sets the count here, so read your bag. See the material compare.
- Sealing and mass matter more than you think. Air gaps at the top plate, around boxes and under the door leak sound straight through; adding mass (a second layer of drywall, resilient channel, decoupling) does the heavy lifting on the STC rating. Insulation is the cavity part of that system, not the whole of it.
- Measure the wall face. Length × height of the one wall you are filling — do not double it for two sides; the batt sits once in the cavity.
This is a quantity count only, not an acoustic-engineering rating — mass, decoupling and sealing set the real STC. Check the product data sheet for the assembly ratings.
Reference table
| Batt R-value | Labeled coverage | Bundles for 200 ft² |
|---|---|---|
| R13 | 88 ft²/bundle | 3 bundles |
| R15 | 67 ft²/bundle | 3 bundles |
| R19 | 75 ft²/bundle | 3 bundles |
| R21 | 58 ft²/bundle | 4 bundles |
| R30 | 58 ft²/bundle | 4 bundles |
| R38 | 40 ft²/bundle | 5 bundles |
For sound work, a heavier batt (mineral wool / safb) that fills the cavity beats a thin one — but coverage per bundle is what sets the bundle count. Read the bag.
Frequently asked questions
How much insulation do I need to soundproof a wall?
Enough batt to fill the stud cavity across the wall face. Divide the wall area by the coverage per bundle and round up — a 200 ft² wall at 88 ft²/bundle is 3 bundles. Fill, do not compress.
What is the best insulation for sound?
Dense mineral-wool (Rockwool) or sound-attenuation (safb) batts outperform light fiberglass for sound, though any full-depth batt helps. The bundle count here depends on the coverage on your bag, not the material.
Will insulation alone soundproof a room?
No. Batt damps cavity resonance, but sealing air gaps and adding mass (extra drywall, resilient channel, decoupling) do most of the work on the STC rating. Treat insulation as one part of the assembly.
Do I count both sides of the wall?
No — count the wall face once. The batt sits once in the stud cavity, so it is length × height of the wall, not doubled for two drywall faces.