There are a couple of ways to answer this question. Most important is for your team to discuss the financial aspect of this. Are you budget constrained? Are you quality monitor constrained?

According to LeapFrog! data, almost 50% of companies monitor 10 or fewer calls per reporting period per agent. Almost 30% of the companies monitor five or fewer.

According to APQC and Response Design best practice studies, best-in-class call centers monitor six to ten calls per reporting period.

Response Design also cautions call centers to document how they are going to use the calls. If the monitored calls are going to be used to determine training needs and/or short term recognition then the numbered monitored each reporting period can be used for this. However, if you are going to use the calls for any type of disciplinary action then you should wait until you have at least 30 calls scored (this can be a rolling average).