How to Calculate Time-Weighted Averages

By Tricia Lobo

Time-weighted averages take into consideration not only the numerical levels of a particular variable, but also the amount of time spent on it. For instance, if workers are exposed to different doses of noise for different amounts of time, we might use time-weighted averages -- acknowledging the differences in the amounts of time spent exposed to different amounts of noise -- to determine a worker's average amount of sound exposure.

Multiply each value by its time weighting. For instance, if a worker is exposed to 86 dB of noise for 13 hours a week, 26 dB of noise for 23 hours a week, and 0 dB of noise for 4 hours a week, you would obtain 86 x 13, 26 x 23 and 0 x 4 (1118, 598, and 0 dB hours, respectively).

Sum the values that you obtained in Step 1. In this case, you will obtain 1716 dB hours.

Add together the time weights to get the total weight. In this case, the total weight is 13 + 23 + 4 = 40 hours.

Divide the value in Step 2 by the total weights in Step 3, to obtain 1716 / 40 = 42.9 dB.

About the Author

Tricia Lobo has been writing since 2006. Her biomedical engineering research, "Biocompatible and pH sensitive PLGA encapsulated MnO nanocrystals for molecular and cellular MRI," was accepted in 2010 for publication in the journal "Nanoletters." Lobo earned her Bachelor of Science in biomedical engineering, with distinction, from Yale in 2010.