US general industry · 5 dB exchange
OSHA noise dose & TWA calculator
Combine measured steady noise periods using OSHA Appendix A’s reference-duration method.
YOUR INPUTS
Set the scope. Enter the data.
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YOUR RESULT
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Enter your data and select Calculate. Your result will show the formula, units and interpretation alongside the definitions and sources below.
No automatic “safe” rating or compliance certificate.
UNDERSTAND THE METRIC
Definition
Noise dose combines the fractions of a reference exposure duration used at each measured sound level. The eight-hour noise TWA is a logarithmic conversion of that dose; it is not an arithmetic average of decibels.
When to use it
Use measured A-weighted, slow-response exposure levels and non-overlapping durations to explore the OSHA general-industry method. It does not measure sound, select hearing protectors or establish complete compliance.
Formula
T = 8 × 2^((90 − L)/5). Dose (%) = 100 × Σ(C/T). Eight-hour TWA (dBA) = 16.61 × log10(dose/100) + 90.
USE IT CONSISTENTLY
Inputs and interpretation
- L is measured dBA, C is hours at that level and T is the reference duration in hours. This tool supports steady levels from 80 to 115 dBA and no more than 24 hours of non-overlapping periods. It does not assess impulse/impact noise or higher levels.
- This uses a 90 dBA criterion level and 5 dB exchange rate. Do not combine this formula with a different criterion level or exchange rate.
- Under 1910.95(c), 50% dose corresponds to the 85 dBA eight-hour hearing-conservation action level. The standard’s 100% reference dose corresponds to 90 dBA for eight hours. All applicable duties still need assessment.
- For hearing-conservation exposure assessment, do not subtract hearing-protector attenuation from these inputs. Enter measured exposure before PPE attenuation.
- Enter all relevant measured periods within this tool’s scope. Unentered or unmeasured exposure is not proven to be zero. This general-industry calculation is not a determination of construction-specific or local-law compliance.
Sources
Technical references checked on 31 October 2026. OSHA sources establish the methods or guidance described above; they do not constitute OSHA approval or endorsement of this calculator.