Repeat rate is the percentage of customers who return for another purchase within a chosen window. The window should suit the trade: 30 days for a cafe or greengrocer, 60 days for a butcher or pet shop, a season for a boutique. A repeat rate of 70 percent over 30 days means seven in every ten customers who bought something in that period came back at least once more inside it.
The hard part for a small shop is knowing who came back at all. Card payments do not say who the customer was, and cash says even less. That is why many owners never measure it, and why a loyalty list is useful even before anyone receives a reward: it turns anonymous sales into named visits for the customers who joined.
In practice
A butcher stamps one stamp per visit and stamps every new member on the day they join. That means any member with two or more stamps has come back at least once since joining. In March, 150 customers joined. At the end of May, the owner goes down the list, finds those 150 by their joined date, and counts how many have two stamps or more: 117. The repeat rate for March joiners over about two months is 117 divided by 150, or 78 percent.
The same count for April joiners, taken at the end of June, comes to 64 percent. A drop like that is a prompt to ask what changed in April. In this shop, a new casual had started on Saturdays and was not stamping returning members, so their counts sat at one. Once that was fixed, the next month's figure came back to 76 percent.
Repeat rate among members is not the same as repeat rate for the whole shop, because members are likely to be the customers who were coming back anyway. Treat it as a health check on the club and on stamping, not as proof that the card created the visits.