Calculator

How long is that noise safe?

Enter a sound level and see the maximum daily exposure under both American standards. They disagree, often by a factor of eight — and knowing which one applies to you matters more than either number on its own.

Arijeet Singh · Builder and maintainer

Built Noise Decibel Meter and maintains its measurement code. Writes up the sound-level references on this site from primary sources — OSHA, NIOSH, WHO and ISO — and states plainly where a browser microphone stops being good enough.

Last reviewed

95 dBA
7095120

OSHA · legal limit

4 hrs

90 dBA PEL, 5 dB exchange rate

NIOSH · health recommendation

1 hr

85 dBA REL, 3 dB exchange rate

Values are for continuous noise over a single day. Impulse noise — gunfire, fireworks, nail guns — is governed separately and is not modelled here.

Which standard applies to you

OSHA publishes a permissible exposure limit of 90 dBA as an eight-hour time-weighted average, set out in 29 CFR 1910.95. It uses a 5 dB exchange rate: every 5 dB rise halves the permitted time. This is an enforceable legal ceiling for American workplaces, and it dates from 1971. A separate action level at 85 dBA obliges employers to run a hearing conservation programme.

NIOSH recommends 85 dBA over eight hours with a 3 dB exchange rate — the rate that actually reflects how sound energy accumulates, since 3 dB is a doubling of intensity. It carries no legal force but is the better guide to whether your hearing is at risk.

The practical rule: if you are protecting your own hearing, follow NIOSH. If you are demonstrating compliance to a regulator, OSHA is the one that is enforceable. Meeting OSHA does not mean your hearing is safe.

Full reference table

Maximum daily noise exposure by sound level under OSHA and NIOSH
Sound level OSHA max NIOSH max Status
80 dBA 8 hrs + 8 hrs + Below both limits
85 dBA 8 hrs + 8 hrs Over NIOSH REL
88 dBA 8 hrs + 4 hrs Over NIOSH REL
90 dBA 8 hrs § 2.5 hrs Over OSHA PEL
91 dBA 7 hrs 2 hrs Over OSHA PEL
92 dBA 6 hrs § 1.6 hrs Over OSHA PEL
94 dBA 4.6 hrs 1 hr Over OSHA PEL
95 dBA 4 hrs § 48 min Over OSHA PEL
97 dBA 3 hrs § 30 min Over OSHA PEL
100 dBA 2 hrs § 15 min Over OSHA PEL
103 dBA 1.3 hrs 8 min Over OSHA PEL
105 dBA 1 hr § 5 min Over OSHA PEL
106 dBA 52 min 4 min Over OSHA PEL
110 dBA 30 min § 1 min Over OSHA PEL
115 dBA 15 min § 28 sec Over OSHA PEL

§ marks a value published directly in 29 CFR 1910.95 Table G-16. Other OSHA figures are computed with the formula in Appendix A of the same standard; the two differ only by the table’s rounding.

Why 3 dB matters so much

The exchange rate is the whole argument between the two standards. A 3 dB increase doubles sound energy, so halving the exposure time keeps the total dose constant — that is the physics, and it is what NIOSH follows. OSHA’s 5 dB rate permits substantially more energy before requiring the same reduction in time.

Move the slider to 100 dBA and the gap is stark: OSHA allows two hours, NIOSH fifteen minutes. Both numbers are correct for what they measure. Only one of them is about your hearing.

Measuring the level you are actually in

This calculator is only as good as the dBA figure you feed it. The free decibel meter on this site gives a live A-weighted reading from your browser in a couple of seconds. Use the average over a representative minute rather than a peak — exposure limits are about sustained level, not the loudest instant.

A browser reading lands within roughly ±2–3 dB, which is close enough to tell an 85 dBA room from a 100 dBA one. It is not close enough for a compliance record — that needs an IEC 61672-1 Class 1 or Class 2 meter. The methodology page covers the limits in detail, and the decibel chart lists typical levels for 50 common sounds.

Measure your actual level, then come back and check it.

Open the decibel meter →

Sources