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Multi-Stud Wall Sound Transmission Class (STC) Estimator

Estimate an approximate STC rating for a multi-layer stud wall assembly from an additive rule-of-thumb point system.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Estimated wall STC rating

44 STC (estimated)

Low confidence

This is an engineering rule-of-thumb ADDITIVE estimate only, not a certified rating — actual STC performance depends on flanking transmission, workmanship, and specific product combinations. Always specify and verify acoustic performance using a manufacturer's actual ASTM E90 lab-tested assembly rating for any acoustic-critical project (e.g. multifamily party walls), never this estimate.

At the values currently entered, the estimated wall stc rating works out to 44 STC (estimated). Note that number of extra gypsum layers (beyond one per side) sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. Confidence on this run is low: check the result against a supplier quote or a professional before ordering or building. Figures are shown for United States, where IRC 2024 is the governing residential reference; switch the market above if you are building elsewhere.

Add the equipment this sizes

This result is a specification — 44 STC (estimated) — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Common acoustic design guide rule of thumb: STC ≈ base single-stud-wall STC (commonly ~33) + resilient channel/decoupling bonus (commonly +8) + cavity insulation bonus (commonly +3) + extra gypsum layer bonus (commonly +2 to +3 per additional layer) — this is a widely-used ADDITIVE ESTIMATION rule, NOT an ASTM E90-standardized predictive method

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Frequently asked questions

How accurate is this STC estimate?
Treat it as a rough rule-of-thumb only, not a certified rating. It is a widely-used additive estimation rule built from commonly cited point bonuses for decoupling, cavity insulation, and extra gypsum layers, not an ASTM E90-standardized predictive method — actual performance also depends on flanking transmission and workmanship.
Can I use this number in a project specification or acoustic compliance submittal?
No — for any acoustic-critical project, such as a multifamily party wall, specify and verify performance using the manufacturer's actual ASTM E90 lab-tested assembly rating for your exact wall makeup, not this estimate.
Where do the bonus point values come from?
They are commonly cited figures from acoustic design guides — for example, roughly +8 for resilient channel/decoupling, +3 for cavity insulation, and +2 to +3 per extra gypsum layer — but real assemblies vary, so confirm against published assembly data for your specific products where possible.