Hi, You can work it out using the following formula: LEP,w = 10log[1/5 Σ10^(LEP,d/10)i] Where i indicates a particular working day, ^ indicates integer values in brackets and Σ indicates that the calculated figures for each day are added together. For an operative who had the following working week: Monday 3 hours LEP,d 93.3 dB(A) Tuesday 3 hours LEP,d 88.3 dB(A) Wednesday 3 hours LEP,d 89.3 dB(A) Thursday 3 hours LEP,d 89.7 dB(A) Friday 3 hours LEP,d 89.7 dB(A) LEP,w = 90.4 dB(A) Hopefully correct but quite likely I’ve made a mistake or use the easy way the HSE noise calculator at: http://www.hse.gov.uk/noise/calculator.htm HSE allow you to calculate exposure over a week rather than over a day if noise exposure varies markedly from day to day eg. If you use noisy powertools on one day of the week but not others. Also you need to make sure you reduce the risk to as low a level as reasonably possible. The guidance states that it is only likely to be appropriate in situations where daily noise exposure on one or two working days is at least 5dB higher than the other days, or the working week comprises 3 or fewer days of exposure. Cheers Steve