What NRR means
The Noise Reduction Rating (NRR) printed on hearing protectors in the US is measured in a laboratory with trained subjects and perfect fit. In everyday use, protection is usually much lower. That's why both OSHA and NIOSH recommend derating the label value before estimating how much noise actually reaches your ears.
OSHA method
Protection (dBA) = (NRR − 7) ÷ 2
The 7 dB correction converts the C-weighted label to A-weighted measurements; dividing by two is OSHA's 50 % safety derating. With a 29 dB earplug: (29 − 7) ÷ 2 = 11 dB of expected protection.
NIOSH method
NIOSH derates by protector type: earmuffs by 25 %, formable (foam) earplugs by 50 % and all other earplugs by 70 %, then subtracts 7 dB for A-weighted measurements.
Typical protectors
| Protector | Typical NRR | Good for |
|---|
| Foam earplugs | 29 – 33 | Power tools, shooting, very loud work |
| Reusable silicone / flanged plugs | 20 – 27 | Workshops, motorsport |
| High-fidelity musician's earplugs | 12 – 22 | Concerts, rehearsals – even reduction |
| Passive earmuffs | 20 – 31 | Lawn care, construction, ranges |
| Electronic / level-dependent earmuffs | 20 – 26 | Shooting, worksites – hear speech |
Double protection
For noise above about 100 dBA, wearing earplugs under earmuffs is recommended. The protection doesn't add up: the combined attenuation is roughly the higher-rated protector plus about 5 dB.
Getting a good fit
- Roll foam plugs into a thin crease-free cylinder, pull the ear up and back, insert, and hold for 20 – 30 seconds while they expand.
- Earmuff seals must sit flat – glasses arms, hair and caps reduce protection.
- Choose a size that fits your ear canal; many brands offer small and large sizes.
- Replace disposable plugs daily and earmuff cushions when they harden or crack.
Don't over-protect
Too much attenuation can isolate workers, hide warning signals and make people remove protectors. Aim for a protected level of about 70 – 80 dBA.
General information only – not medical or legal advice.
Frequently asked questions
How do you calculate real NRR protection?
OSHA's method: subtract 7 from the NRR and divide by 2 for dBA measurements. A 33 NRR plug gives about 13 dB of real-world protection.
Does double hearing protection add the NRRs together?
No. Combined protection is roughly the higher NRR plus 5 dB.
What NRR do I need for shooting?
Gunshots exceed 140 dB. Use the highest-rated protection available, ideally foam earplugs under earmuffs.
Are musician's earplugs good enough for concerts?
Yes for most concerts – they reduce levels evenly by about 12 – 22 dB while keeping music clear.
Why is real protection lower than the label?
Lab tests use perfect fit and trained users; in practice fit, movement and comfort reduce protection.
About NRRcheck
NRRcheck is an independent, free calculator using published OSHA and NIOSH methods for estimating hearing protector performance. Real protection depends on fit and training. It is general information, not medical or legal advice. We are not affiliated with any hearing protection brand.
Every formula on this page runs entirely in your web browser. The numbers you type are never uploaded, stored or shared. Our goal is simple: give you an honest starting point so you can compare product specifications with confidence and avoid paying for capacity you do not need – or buying something too small to do the job.
The methodology combines widely published engineering rules of thumb, manufacturer data sheets and the electrical code practices that installers use every day. We review the assumptions regularly and update the calculator when typical product specifications change.
Privacy Policy
Last updated: October 28, 2026
This Privacy Policy explains how NRRcheck ("we", "us") handles information when you visit this website. By using the site you agree to this policy.
Information we collect
We do not require registration and we do not ask for your name, address or payment details. Values entered into the calculator are processed locally in your browser and are not transmitted to our servers. Like most websites, our hosting provider may automatically record standard server log data such as IP address, browser type, referring page and time of visit for security and performance purposes.
Cookies and advertising
We use Google AdSense to show advertisements that keep this tool free. Third-party vendors, including Google, use cookies to serve ads based on a user's prior visits to this website or other websites. Google's use of advertising cookies enables it and its partners to serve ads to users based on their visit to this site and/or other sites on the Internet. You may opt out of personalized advertising by visiting Google Ads Settings, or opt out of some third-party vendors' use of cookies for personalized advertising at www.aboutads.info (US) or www.youronlinechoices.eu (Europe). To learn more, see How Google uses information from sites or apps that use its services.
Visitors from the European Economic Area, the United Kingdom and Switzerland are shown a consent message powered by a Google-certified consent management platform, where you can accept, reject or manage cookie choices. You can change your choices at any time from the privacy link displayed by that message. Some visitors may also be offered the option to view a short ad or complete another offer in exchange for access to the content; this choice is provided by Google and is entirely optional where alternatives are offered.
Analytics
We may use privacy-friendly, aggregated statistics to understand which features are used. These statistics do not identify you personally.
Your rights
Depending on where you live (for example under the GDPR or the CCPA/CPRA), you may have the right to access, correct or delete personal data and to object to certain processing. Because we do not keep personal data from the calculator, most requests can be handled by clearing cookies in your browser. For any other request, contact us at the address above.
Children
This site is intended for a general adult audience and is not directed at children under 13. We do not knowingly collect personal information from children.
Changes to this policy
We may update this policy from time to time. The date at the top of this section shows when it was last revised.
Terms of Use & Disclaimer
The calculator and articles on this website are provided free of charge for general information and educational purposes only. Results are estimates based on typical values and simplifying assumptions; real-world performance depends on the specific product, installation, climate, wiring and how you use your equipment.
Nothing on this site is professional engineering, electrical or financial advice. Always follow the manufacturer's instructions and local electrical codes, and have permanent installations, transfer switches and grid-connected systems designed and installed by a licensed electrician or qualified installer. Never operate fuel-burning generators indoors or in enclosed spaces – carbon monoxide can kill within minutes.
The site is provided "as is" without warranties of any kind. To the fullest extent permitted by law, NRRcheck is not liable for any loss or damage arising from the use of, or reliance on, the information or results provided. Product and brand names mentioned belong to their respective owners and are used for identification only. You may use the calculator for personal and commercial purposes, but you may not copy or republish the site content without permission.
NRRcheck