Noise dose calculator: daily noise exposure from levels and durations, % dose, 8-hour TWA and LEX,8h (3 dB and 5 dB exchange rates)

What it does

Loud noise damages hearing according to how loud it is and how long it lasts. Workplace rules turn this into a daily noise dose: 100 % is the most a worker should get in a day, for example 85 dB(A) for 8 hours. Every few decibels louder halves the time allowed: 3 dB under the equal-energy rule (NIOSH, the EU, the UK and many others), 5 dB under the US OSHA rules.

This calculator takes a list of tasks with their A-weighted level and duration, and works out:

• the allowed time at each level and each task’s share of the dose;
• the total dose in per cent, and the 8-hour time-weighted average (TWA) that gives the same dose;
• LEX,8h, the energy average normalised to 8 hours used in the EU and UK;
• the time left at the loudest task before the dose reaches 100 %.

How to use it

1. Pick a preset or type your own criterion level, exchange rate, threshold (levels below it are not counted; leave empty for none) and criterion duration.
2. List the day’s tasks, one per line: an optional name, the level in dB(A) and the time. Choose minutes or hours; h:mm also works. You can also open a CSV or Excel file, such as a dosimeter log.
3. Read the dose, TWA and LEX,8h, the chart of allowed time against level, and the table. Download the table as CSV, or the report as an image, PDF or Word file.

Worked example

The made-up day is 60 minutes of grinding at 95 dB(A), 300 minutes on an assembly line at 85, an hour in a break room at 70 and an hour on a forklift at 90. Under the NIOSH preset (85 dB(A), 3 dB, threshold 80) the page shows Daily dose 228 % (TWA 88.6 dB(A)), flagged as over the criterion. Grinding alone is allowed only 48 minutes at 95 dB(A), so its hour is 126 % of the dose; the break room is below the threshold and counts as nothing. LEX,8h is also 88.6 dB(A).

Switch to the US OSHA PEL preset (90 dB(A), 5 dB, threshold 90) and the same day is a 38 % dose (TWA 82.9 dB(A)), because the 85 dB(A) work no longer counts and each 5 dB only halves the time. With the OSHA action level preset the dose is 138 % (TWA 87.3 dB(A)). The same day can pass one rule and fail another, which is why you must use the rule that applies where you work.

The tests also reproduce the worked example in OSHA’s Appendix A: 110 dB(A) for 15 minutes, 100 for 30 minutes and 90 for 90 minutes give a dose of 93.75 %, which the rule rounds to 94 %.

Tips

• Use LAeq values for each task, not the loudest reading.
• Halving the time at the loudest task often does more than any other change.
• Hearing protection is not included; its real-world protection is often much less than the label says.

FAQ

Which preset should I use? The one in the rules that apply to your workplace. Rules differ between countries, provinces and states, and change; check your local rules and the official source.

Is this a noise assessment? No. It does arithmetic on the levels you type. For study and planning, not a substitute for professional judgement or a proper noise assessment.

Last updated 2026-11-09.