Intended Audience:
Marketing Directors, RevOps Leads, and Founders
When to Use:
Monthly to evaluate campaign ROI and subscriber lifecycle velocity.
Prerequisites:
Google Analytics 4 / CRM tracking and ESP delivery reporting
Format & Access:
Open Markdown / Direct Copy (No form gating)
Actionable Resource ContentLast Reviewed: September 2026
## Essential Lifecycle KPI Formulas
### 1. Click-to-Open Rate (CTOR)
- **Formula:** (Unique Clicks / Unique Opens) * 100
- **Purpose:** Measures content relevance and offer resonance without Apple MPP distortion.
### 2. Qualified Inquiry Rate (QIR)
- **Formula:** (Sales-Accepted Inquiries / Total Campaign Recipients) * 100
- **Purpose:** Evaluates whether campaigns attract genuine buyers or vanity signups.
### 3. List Churn Rate
- **Formula:** (Unsubscribes + Hard Bounces + Spam Complaints) / Total List Size * 100
- **Benchmark:** Keep monthly list churn under 1.5% to maintain database health.
### 4. Revenue Per Subscriber (RPS)
- **Formula:** Total Attributed Revenue / Active List Size
- **Purpose:** Tracks long-term commercial database expansion.