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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 in United States units and terminology, and each formula’s basis 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). Confidence on this run is low: check the result against a supplier quote or a professional before ordering or building. Figures are shown in United States units and terminology; 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 — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.

Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

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.