Work out your daily noise dose: add each noisy part of your day, such as a lawn mower, power tools or a concert, with its level in dB(A) and how long it lasts. You get your dose and 8-hour average under NIOSH, OSHA and EU/UK rules side by side, with hearing protection and the time you have left.
Noise Exposure Calculator
Add each noisy activity with its level and time to get your daily noise dose under NIOSH, OSHA and EU/UK rules.
NIOSH recommended limit
79%
8-hour TWA: 84.0 dB(A)
Within the recommended daily limit, but close to it.
OSHA US legal limit
25%
8-hour TWA: 80.0 dB(A)
Within the legal limit. Action-level dose 25%: no hearing conservation programme needed.
EU / UK daily exposure
84.0 dB(A)
LEX,8h: 79% of the energy of 85 dB(A) for 8 hours
Above the lower action value (80 dB(A)): information, training and hearing protection must be available.
Bars run to 200% of the daily dose (the line marks 100%).
At 90 dB(A) you could add about 31 min before reaching the NIOSH limit.
| Activity | Level at the ear | Time | NIOSH safe time | NIOSH dose | OSHA safe time | OSHA dose |
|---|---|---|---|---|---|---|
| Petrol lawn mower | 90 dB(A) | 2 h | 2 h 31 min | 79% | 8 h | 25% |
A screening estimate, not a workplace noise assessment. Levels are typical values at the ear; measure your own for accuracy. Levels above 115 dB(A) are not permitted under OSHA, and impulse noise (gunshots, hammering) needs a peak measurement.
Related Tools
- Sound Decibel Meter
Measure the level of each activity in dB(A) before you enter it.
- Noise Monitor & Logger
Log a whole shift or event and get the average level (Leq).
- Decibel Chart
Typical levels for over 20 everyday and workplace sounds.
- Decibel Calculator
Average several readings or add machines running together.
- Online Hearing Test
Check both ears if you work in noise or notice ringing.
How to Use the Noise Exposure Calculator
- Enter the first activity: its A-weighted level at your ear and how long it lasts. Use a measured value if you can, or pick a common noise from the list.
- Add each other noisy activity of the day. Quiet periods below 80 dB(A) barely change the result, so you can leave them out.
- If you wear earplugs or earmuffs, choose the protection type and enter the NRR from the package.
- Read the three results. A dose above 100% means the day exceeds that limit. The table shows how much each activity contributes, so you know which one to cut first.
NIOSH vs OSHA vs EU Noise Limits
| NIOSH REL (US, recommended) | OSHA PEL (US law) | EU / UK (law) | |
|---|---|---|---|
| 8-hour limit | 85 dB(A) | 90 dB(A) | Action values 80 and 85 dB(A); limit value 87 dB(A) with protection |
| Exchange rate | 3 dB | 5 dB | 3 dB (energy average) |
| Safe time at 100 dB(A) | 15 minutes | 2 hours | 15 minutes to reach 85 dB(A) LEX,8h |
| Other triggers | – | Action level 85 dB(A): hearing conservation programme; no continuous exposure above 115 dB(A) | Peak action values 135 and 137 dB(C), limit 140 dB(C) |
| Levels counted | 80 dB(A) and above | 90 dB(A) and above (PEL); 80 dB(A) and above (action level) | All levels |
The main difference is the exchange rate: how many decibels halve the safe time. NIOSH and the EU use 3 dB because every 3 dB doubles the sound energy (the equal-energy rule). OSHA’s 5 dB rule dates from 1971 and allows much more time at high levels. NIOSH estimates that a working lifetime at the OSHA limit leaves about a quarter of workers with material hearing loss, compared with 8% at its own 85 dB(A) limit. Our noise exposure time limits guide covers the rules in full.
How the Noise Dose Is Calculated
For each activity the calculator finds the allowed time T at that level, then adds up the fractions of allowed time you used:
- Dose D = 100 × (C₁/T₁ + C₂/T₂ + …), where C is the time spent and T the allowed time.
- NIOSH: T = 8 h ÷ 2^((L − 85) ÷ 3); 8-hour TWA = 10 × log10(D ÷ 100) + 85.
- OSHA: T = 8 h ÷ 2^((L − 90) ÷ 5); TWA = 16.61 × log10(D ÷ 100) + 90.
- EU/UK: LEX,8h = 10 × log10(Σ (t ÷ 8 h) × 10^(L ÷ 10)).
Worked example: 2 hours of lawn mowing at 90 dB(A) plus 4 hours of workshop noise at 85 dB(A). NIOSH: 2 h of the 2 h 31 min allowed (79%) plus 4 h of 8 h (50%) = 129%, a TWA of 86.1 dB(A), over the limit. OSHA PEL: only the 90 dB(A) part counts, 2 h of 8 h = 25%. But OSHA’s action-level dose also counts the 85 dB(A) hours (4 h of 16 h = 25%), giving 50%: exactly the 85 dB(A) TWA at which a hearing conservation programme becomes mandatory. EU/UK: LEX,8h = 86.1 dB(A), above the upper action value, so hearing protection must be worn.
Safe Exposure Time by Noise Level
| Level dB(A) | NIOSH (3 dB rule) | OSHA (5 dB rule) |
|---|---|---|
| 85 | 8 h | 16 h |
| 88 | 4 h | 10 h 33 min |
| 90 | 2 h 31 min | 8 h |
| 91 | 2 h | 6 h 58 min |
| 94 | 1 h | 4 h 36 min |
| 95 | 48 min | 4 h |
| 97 | 30 min | 3 h 2 min |
| 100 | 15 min | 2 h |
| 103 | 7.5 min | 1 h 19 min |
| 105 | 4.7 min | 1 h |
| 110 | 1.5 min | 30 min |
| 115 | 28 s | 15 min (maximum) |
Times are per day, for the whole dose at one level. When you are exposed to several levels, the fractions add up, which is exactly what the calculator does. For a quick visual overview, see the safe noise levels chart.
Hearing Protection and the NRR
The Noise Reduction Rating (NRR) on US earplug and earmuff packages is measured in a lab with ideal fit, and real-world protection is usually much lower. The calculator uses OSHA’s method for A-weighted levels: subtract 7 from the NRR and halve the result, so an NRR 33 foam earplug is counted as a 13 dB reduction. With earplugs and earmuffs together, add 5 dB to the better protector’s derated value. If you know your real attenuation, for example from a fit test, choose that option instead.
Fit matters more than the number on the package: a foam earplug rolled tightly and inserted deep can beat a loosely fitted earmuff with a higher NRR. In the EU and UK, protectors carry an SNR value instead, measured differently; enter a realistic attenuation of about SNR minus 4 to 5 dB, as UK guidance allows for real-world use.
Measuring the Levels to Enter
The result is only as good as the levels you enter. Measure at ear height, where you normally stand, with A-weighting (why dB(A)). For noise that changes, such as a shift in a workshop, log it and use the average (Leq) rather than a single reading. Our guide on how to measure decibels explains the method, and a calibrated microphone makes a phone far more accurate. For legal compliance, employers use personal dosimeters or Class 1 or 2 meters; see sound level meter vs decibel meter.
Frequently Asked Questions
What is a noise dose?
It is the share of your daily allowance you have used. 100% is the most a limit allows; 50% means half the allowance; 200% means twice the limit, equal to 3 dB above it under NIOSH.
Is 85 dB for 8 hours safe?
It is the NIOSH recommended maximum, so it is the limit, not a completely safe level: NIOSH estimates an 8% excess risk of hearing loss over a working lifetime at 85 dB(A).
Why does OSHA allow more time than NIOSH?
OSHA uses a 90 dB(A) limit with a 5 dB exchange rate, set in 1971. NIOSH’s 1998 criteria use 85 dB(A) with 3 dB, based on newer research, so they are more protective.
Does headphone listening count?
Yes, sound is sound. For music, the WHO safe listening standard uses a weekly allowance equal to 80 dB for 40 hours; see is 80 dB loud?. You can enter headphone time as an activity to see its daily share.
What should I do if my dose is over 100%?
Cut the time at the loudest activity, move further from the source (each doubling of distance lowers the level by about 6 dB), use quieter equipment, or wear well-fitted hearing protection.