Email List Growth Calculator

A list grows by a fixed number and shrinks by a percentage. Signups arrive at roughly the rate your acquisition produces them. Churn takes a slice of whatever the list has become. Early on, signups dwarf the slice and the list climbs quickly. As the list gets bigger, the slice gets bigger too, until the month churn removes exactly as many people as signups add. That is the ceiling: monthly signups divided by monthly churn rate. With 800 signups a month and 2.5 percent churn, the ceiling is 32,000 subscribers, no matter how long you wait.

This is why a list that grew fast in year one feels stuck in year three, and why the common response, spending more on acquisition, is only half the answer. Doubling signups doubles the ceiling. Halving churn also doubles it, usually for less money, because it is a matter of sending things people want to read at a cadence they can keep up with. The calculator lets you test both. Change the churn rate and watch the ceiling move; change signups and watch how long it takes to get there.

The optional signup growth rate models a list where acquisition itself is improving, say a referral programme that adds a few percent more signups each month. When signups compound, there is no fixed ceiling, but the same dynamic still applies: growth slows whenever churn losses approach signups, and the numbers in the table show exactly when that happens.