About the Noise Exposure Calculator
This noise exposure calculator works out how much of your safe daily sound "allowance" you use up. Enter up to three noise levels in A-weighted decibels (dBA) and how long you spend at each, and it returns your daily noise dose as a percentage, the equivalent 8-hour time-weighted average (TWA), and the maximum safe time at each level.
Choose between two US limits. The NIOSH recommended exposure limit (REL) is 85 dBA for 8 hours with a 3 dB exchange rate — every 3 dB increase halves the safe time — and is the protective standard most hearing experts use. The OSHA permissible exposure limit (PEL) in 29 CFR 1910.95 is 90 dBA for 8 hours with a 5 dB exchange rate, and is the legal minimum for most US workplaces; OSHA’s hearing conservation "action level" is a 50% dose (85 dBA TWA).
It suits workers, musicians, DIYers, concert-goers and anyone checking headphone habits. A dose of 100% means you have reached the limit for the day; anything above that raises the risk of permanent noise-induced hearing loss. Levels below 80 dBA are not counted: both NIOSH and OSHA’s hearing-conservation monitoring integrate sound from 80 dBA upward (OSHA’s strict PEL compliance check counts only 90 dBA and above, so this tool can slightly overstate an OSHA PEL dose when much of the day is at 80–89 dBA). Sound-level apps give rough readings only — a calibrated meter or dosimeter is needed for compliance work.
With the default inputs, the daily noise dose is 125%. Change any value above to recalculate instantly.
How to use the noise exposure calculator
- 1Pick the NIOSH (protective) or OSHA (legal US workplace) limit.
- 2Enter the sound level of each noisy activity in dBA.
- 3Enter how many hours a day you spend at each level.
- 4Read your daily dose — 100% means you have hit the limit.
- 5Check the safe time per level and the table to plan breaks or hearing protection.
Formula and method
Each sound level has a reference duration T — the time that would use exactly 100% of the daily allowance. It is 8 hours at the criterion level Lc and halves for every q decibels above it: Lc = 85 dBA and q = 3 dB for NIOSH, Lc = 90 dBA and q = 5 dB for OSHA (Table G-16a of 29 CFR 1910.95). The daily dose D adds up the fraction of allowance used by each exposure: time spent Cᵢ divided by the reference duration Tᵢ.
The 8-hour TWA converts the dose back into the constant level that would give the same dose over 8 hours: TWA = 16.61 × log₁₀(D/100) + 90 for OSHA and 10 × log₁₀(D/100) + 85 for NIOSH. Sounds below 80 dBA are ignored (the lower integration limit in NIOSH 98-126 and in OSHA’s hearing-conservation monitoring rule, 1910.95(d)(2)(i)), and levels are A-weighted with slow response. Both limits are as published and in force in 2026.
- L
- A-weighted sound level, dBA
- Lc
- Criterion level: 85 dBA (NIOSH) or 90 dBA (OSHA)
- q
- Exchange rate: 3 dB (NIOSH) or 5 dB (OSHA)
- C
- Hours spent at a level
- D
- Daily noise dose, %
Worked examples
NIOSH: 4 h at 85 dBA, 45 min at 94 dBA, 3 h at 70 dBA
Under NIOSH, 85 dBA is allowed for 8 h, so 4 h uses 50%. At 94 dBA the allowance is 8 ÷ 2³ = 1 hour, so 45 minutes uses another 75%. The 70 dBA period does not count. The total of 125% equals an 8-hour TWA of 85 + 10 × log₁₀(1.25) ≈ 86.0 dBA — over the limit.
OSHA: the same day
OSHA allows 85 dBA for 16 h, so 4 h is 25%. At 94 dBA T = 8 ÷ 2^0.8 = 4.59 h, so 0.75 h adds 16.3%. The total of 41.3% (TWA ≈ 83.6 dBA) is within the PEL and below the 50% action level — the same day that fails the NIOSH limit.
NIOSH: a 2-hour concert at 100 dBA
At 100 dBA NIOSH allows just 8 ÷ 2⁵ = 0.25 h (15 minutes). Two hours is eight times that, a dose of 800% — high-fidelity earplugs are strongly advised.
Frequently asked questions
How long can I safely listen to 85 dB?+
NIOSH recommends no more than 8 hours a day at 85 dBA. Because of the 3 dB exchange rate, the safe time halves with each 3 dB: 4 hours at 88 dBA, 2 hours at 91 dBA, 1 hour at 94 dBA and about 15 minutes at 100 dBA.
What is the difference between the NIOSH and OSHA noise limits?+
OSHA’s legal limit is 90 dBA for 8 hours with a 5 dB exchange rate, so it allows 4 hours at 95 dBA. NIOSH recommends 85 dBA with a 3 dB exchange rate, allowing only about 47 minutes at 95 dBA. NIOSH’s limit is more protective.
What does a noise dose of 100% mean?+
A 100% dose means you have received the maximum daily sound energy the chosen limit allows. Higher doses increase the risk of permanent hearing damage, and doses above 100% under OSHA rules mean a workplace is out of compliance unless controls are used.
What is the OSHA action level?+
Under 29 CFR 1910.95, an 8-hour TWA of 85 dBA — equivalent to a 50% dose — is the action level. Employers must then run a hearing conservation program with monitoring, annual hearing tests, training and available hearing protectors.
How loud are everyday sounds?+
Typical levels are roughly 60 dBA for conversation, 80–90 dBA for a lawn mower or busy traffic, 95–100 dBA for power tools or a motorcycle, and 100–110 dBA at concerts or clubs. Actual levels depend heavily on distance.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.