From a Call Centre and Staffing Point of view the primary elements considered are as follows:
- Average Talk Time
- Calls/per specified period (15min is a good benchmark)
- Specified Service Metrics or SLA (ie. 80/20 <- 80% of calls answered in 20s or less etc...) ... correspondingly, you want to consider your abandon %'age here also. Are you willing to accept that some of your customers will hang up? If so, how many & consider what impact that will have on your business in the long run!
Some Good Free Erlang 'C' Calculators -