Understanding retention metrics is critical for any SaaS founder or product leader. These five interconnected metrics tell you whether your business is actually growing and help you make data-driven decisions about customer health, growth, and profitability.
This glossary breaks down the most important SaaS retention metrics, explains how they're calculated, and shows how they relate to each other. Whether you're optimizing your churn rate or benchmarking against industry standards, you'll find clear definitions and practical examples below.
NRR measures whether your existing customer base is growing or shrinking in value—it's the single most important metric for SaaS growth because it shows if you're expanding revenue faster than you're losing it.
Scenario: You start January with $100k MRR
NRR = ($120k - $0) / $100k × 100 = 120%
This means for every dollar you had at the start, you retained $1.20 from existing customers.
GRR isolates the effect of churn alone, making it useful for diagnosing whether your core product retention is healthy.
Using the same scenario as NRR example:
GRR = ($100k - $15k) / $100k × 100 = 85%
| Situation | Focus On | Why |
|---|---|---|
| You have low churn but high expansion | GRR | Churn isn't your problem; you're doing well |
| You have high churn but low volume | GRR | Focus on fixing the churn first |
| You're scaling and need a growth metric | NRR | This shows your true business health |
| You're an early-stage startup | GRR | Build a retention foundation first |
This is simpler than NRR/GRR—it measures customer count, not revenue.
Retention Rate = (500 - 25 - 50) / 500 × 100 = 85%
It's the ratio of new ARR (or MRR) to sales & marketing spending in the previous quarter.
Q2 metrics:
Magic Number = ($500k - $300k) / $250k = 0.8
This means you're generating $0.80 of new ARR for every dollar spent on sales & marketing in the previous quarter—decent but not amazing.
| Aspect | GRR | NRR |
|---|---|---|
| What it includes | Churn only | Churn + Expansion |
| Formula | (MRR - Churn) / Starting MRR | (MRR - Churn + Expansion) / Starting MRR |
| What it tells you | Product stickiness | True business health |
| Typical range | 85-98% | 100-150% |
| When to focus on it | Diagnosing retention problems | Evaluating growth potential |
Month 1:
GRR = 90%
Your core product is retaining 90% of customers (10% monthly churn)
NRR = 110%
But with expansion, you're actually growing revenue by 10%
✓ High GRR (95%+) + High NRR (120%+)
Healthy churn + strong expansion = Best case scenario
⚠ High GRR (95%+) + Low NRR (100-105%)
Good product stickiness, but limited expansion opportunities. Focus on upselling.
⚠ Low GRR (85%) + High NRR (110%+)
Significant churn, but expansion is making up for it. This is risky—churn will eventually catch up.
✕ Low GRR (85%) + Low NRR (95%)
Major problem. Your business is contracting. Focus on churn reduction immediately.
GRR (Baseline Retention) + Expansion Revenue = NRR (True Growth Metric)
Think of it like this:
| Metric | Why It Matters | Your Action |
|---|---|---|
| GRR | Diagnoses churn problems | Target: 90%+ |
| NRR | Predicts long-term success | Target: 110%+ |
| Retention Rate | Simplest health check | Use for quick diagnostics |
| Magic Number | Validates growth efficiency | Target: 0.75+ (aim for 1.0+) |