Email List Health & Decay Calculator
Analyze your email list health and predict how it decays over time.
Calculate engagement rate, projected list size in 6 and 12 months, and revenue at risk.
How It Works
An email list is a depreciating asset. Even without sending a single email, your list loses roughly 20–25% of its effective value every year as subscribers change jobs, abandon email addresses, lose interest, or unsubscribe. This process is called list decay, and understanding it is essential for realistic revenue planning.
Key metrics this calculator tracks:
Engagement Rate = (Active subscribers ÷ Total subscribers) × 100 Active is defined as anyone who has opened at least one email in the last 90 days. This is your true audience size.
| Engagement Rate | Grade | Health Status |
|---|---|---|
| 25%+ | A | Excellent, highly engaged list |
| 15–24% | B | Good, healthy for most industries |
| 10–14% | C | Poor, needs re-engagement work |
| Under 10% | F | Danger, serious deliverability risk |
Net Monthly Change = New subscribers − (Total subscribers × Monthly unsubscribe rate)
Why inactive subscribers hurt you:
When a large percentage of your list never opens emails, inbox providers (Gmail, Outlook, Apple Mail) notice.
High non-open rates read as low-value content, and more of your mail starts landing in spam, including mail to the people who do want it. This is inbox placement degradation, and it is one of the commonest reasons email revenue collapses with no obvious cause.
Industry benchmarks:
- Average open rate: 20–25% across all industries
- Average monthly unsubscribe rate: 0.1–0.5%
- Re-engagement campaigns: typically recover 5–15% of inactive subscribers
- Good list growth rate: replacing churn plus adding 2–5% net growth monthly
Double opt-in vs. single opt-in: Double opt-in (requiring subscribers to confirm their email) typically produces a list that is 20–30% smaller but with 40–60% higher open rates. The smaller, more engaged list usually outperforms in revenue per subscriber.
List cleaning strategy:
If your engagement rate is below 15%, run a re-engagement campaign.
Send one direct “are you still interested?” email with a clear call to action, and remove anyone who does not respond within 30 days. Your list gets smaller and your deliverability and open rates get better, which is a trade worth making every time.
Revenue at risk: If you send email campaigns for revenue purposes, list decay directly costs money. This calculator estimates annual revenue at risk based on your churn rate and revenue per send.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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