Enter a noise level and exposure time to get your daily noise dose under both OSHA's PEL (90 dBA criterion, 5-dB exchange rate) and NIOSH's REL (85 dBA criterion, 3-dB exchange rate), plus the maximum allowed duration at that level and what an earplug or muff's NRR actually delivers after field derating.
How the math works
Both limits allow 8 hours at their criterion level and halve (or double) the allowed time with each exchange-rate step. OSHA's permissible exposure limit uses 90 dBA with a 5-dB exchange: 8 h at 90, 4 h at 95, 2 h at 100. NIOSH's recommended limit uses 85 dBA with a 3-dB exchange — the physics-honest doubling rate — so: 8 h at 85, 4 h at 88, 2 h at 91. Dose is time-at-level divided by allowed-time, expressed as a percentage; 100% is the limit. OSHA separately sets an action level at 85 dBA (8-hour TWA) that triggers a hearing conservation program under 29 CFR 1910.95.
Common levels to try
Typical values from our decibel levels chart: circular saw ~100–105 dBA, angle grinder ~95–105, chainsaw ~105–115, impact wrench ~100, shop vacuum ~85–95, tractor cab ~85–95, concert ~100–110. At 100 dBA, OSHA allows 2 hours unprotected; NIOSH allows 15 minutes.
Picking protection once the number says you need it
Match the derated NRR to your overexposure, then pick a format workers will actually wear all shift: earplugs (see best foam earplugs and disposable picks), ear muffs (construction picks), or electronic muffs that pass speech and range commands. The full range lives in the hearing protection collection, and when do you need hearing protection walks the decision from scratch.
This calculator provides general guidance using the published OSHA PEL and NIOSH REL formulas — it is not a compliance determination, dosimetry, or medical advice. Workplace programs need measured TWA data and a qualified professional. WC Safety participates in the Amazon Associates Program; product links on this site may earn us a commission.