What it is
Retention is calculated over a period, typically 12 months. The formula: number of active members at end of the period divided by number at the start, with new members joining during the period excluded. The inverse metric is churn. Industry-typical annual retention is around 75 percent.
Why it matters
A small change in percentage translates into a large change in revenue. When new member acquisition through marketing and sales typically costs hundreds of euros, and the monthly fee is a few tens of euros, the member has to stay on average more than a year before acquisition cost is recovered. Improving retention by five percentage points usually delivers more bottom line than adding ten new members per month.
Where retention comes from
Retention is built on three things: perceived value (does the member get a real workout without crowding and broken equipment), emotional bond (staff, community, routine), and switching cost (how much would they feel they're losing by leaving).
In GymPlus network data, members who join in January start churning as early as the fourth week, with the bleed slowing through May. Selectorized strength machines are the network's strongest single predictor of January retention: if a new member finds a path to those machines in the first weeks, they are more likely than others to stay.
How to improve it with data
Measure retention monthly and as cohorts by acquisition month. Identify drop-off points, most often in the first and third month. Combine retention data with capacity utilization, peak-hour load, and equipment fault data: a gym crowded twice a week, or a popular machine repeatedly broken, are exit drivers that do not show up in sales reports but show up in analytics.