Free tool

Call review sample size calculator

Reviewing every call is not possible and reviewing a handful tells you very little. This works out how many you need for a score with a stated margin of error.

Calls per agent per monthRoughly how many calls one agent handles.Number of agentsConfidence levelHow often the true figure falls inside the margin below.Margin of errorHow close the score needs to be, in percentage points.Minutes to review one callListening, scoring and writing the note.

Reviews per agent

per month · 19.5% of their calls

Reviews in total

780

across 10 agents

Reviewer time

hours per month

How this is worked out

This is Cochran's sample size formula with a finite population correction — the standard way to size a sample for estimating a proportion when the population is small enough for its size to matter.

It assumes the worst case for variability, a 50% pass rate, because a team that has not been measuring does not yet know its real one. If your pass rate is already known and much higher, the sample needed is smaller than this.

It also assumes the calls you review are picked at random. Reviewing whichever calls are easiest to find, or only the ones somebody complained about, breaks the arithmetic — the sample no longer represents the whole.