~1 min read
Email list growth is one of the most valuable assets a bootstrapped business can build. Unlike social media followers or paid ad audiences, your email list is an asset you own. But a list that isn't growing is decaying — even with zero new subscribers, unsubscribes and inactivity shrink it every month.
The growth formula
Net monthly growth = New subscribers - (List size x Monthly churn rate)
If you have 10,000 subscribers with 3% monthly churn, you lose 300 subscribers/month from your existing base. To grow, you need more than 300 new subscribers per month.
List decay is compounding
At 3% monthly churn, a list with no new subscribers loses 31% of its size per year. At 5% monthly churn, it loses 46%. This is why email marketers obsess over re-engagement campaigns and sunset policies — inactive subscribers inflate your list size while damaging deliverability.
Industry benchmarks
| Metric | Good | Average | Poor |
|---|---|---|---|
| Monthly churn | < 1.5% | 2-3% | > 4% |
| Open rate | > 30% | 20-25% | < 15% |
| List growth rate | > 5%/mo | 2-4%/mo | < 1%/mo |
Frequently asked questions
What does this calculator do? Calculate email list growth rate, net monthly growth, and time to reach your target list size.