Client retention is how many of your clients keep coming back. It is usually measured over a set period: of the clients who visited in one quarter, how many returned in the next, or of the new clients in a month, how many came for a second visit within a normal interval for their service. A cut client who returns within ten weeks is retained. One who has not been seen in six months probably is not.
Retention matters more than almost any other number in a service business, because a returning client costs nothing to find. Every client who drifts away has to be replaced by a new one, and new clients come with a consultation, a longer first appointment and more uncertainty about whether they will like the result.
In practice
A barbershop counts 120 new clients over three months. By the end of the following quarter, 66 of them have been back at least once, so first-visit retention is 66 out of 120, or 55%. Of the regulars who came in during the first quarter, 310 of 350 came back, about 89%.
The gap between those two figures is where the work is. Regulars are happy; new clients are not yet regulars. The usual fixes are cheap: offer the second appointment before the first one ends, send a thank-you text the day after with the booking link, and make the second visit easy to request at any hour. Measure your rebooking rate at the same time, since clients who leave with a next appointment are far more likely to be counted as retained.
Note the reasons when you learn them. A client who moved interstate is not a failure. A client who did not like her colour and never said so is a lesson, and sometimes the sign of a consultation that was too short.