SaaS Metrics Explained: MRR, ARR, Churn, LTV, CAC, and NRR
A plain-English explanation of the metrics every SaaS founder needs to understand — what they measure, how to calculate them, and what good looks like at...
SaaS metrics have their own vocabulary. Investors speak it fluently; most early-stage founders learn it reactively, after a confused conversation with an investor or a fellow founder. Understanding these metrics isn't just useful for fundraising — it's how you diagnose what's actually happening in your business.
This is the plain-English version.
Quick answer: The six metrics every SaaS founder must track are MRR (sum of active monthly subscriptions), MRR churn rate (churned MRR ÷ starting MRR), LTV (ARPU ÷ monthly churn rate), CAC (total acquisition spend ÷ new customers), LTV:CAC ratio (target 3:1 or better), and NRR (net revenue retention — above 100% means existing customers are growing revenue even without new signups). Monthly churn under 2% and NRR above 100% are the key health thresholds to aim for.
MRR — Monthly Recurring Revenue
What it is: The predictable monthly revenue from all active subscriptions.
How to calculate it: Sum of all active customer monthly subscription amounts.
If you have 10 customers paying $100/mo and 5 paying $300/mo, your MRR is:
- (10 × $100) + (5 × $300) = $1,000 + $1,500 = $2,500 MRR
The components of MRR:
- New MRR: Revenue from customers who just signed up this month
- Expansion MRR: Revenue from existing customers who upgraded
- Churned MRR: Revenue lost from customers who cancelled
- Contraction MRR: Revenue lost from customers who downgraded
Net New MRR = New MRR + Expansion MRR - Churned MRR - Contraction MRR
This is the number that shows whether your business is growing or contracting each month.
Why it matters: MRR is the most important single number for early-stage SaaS. It's predictable (you know roughly what next month looks like), it compounds, and it's the number that determines when you can pay yourself and when you're default alive.
ARR — Annual Recurring Revenue
What it is: MRR × 12. Annualizes your recurring revenue for easier comparison and investor communication.
How to calculate it: MRR × 12. If your MRR is $10,000, your ARR is $120,000.
Important: ARR is not your annual revenue — it's your annualized run rate. If you signed up a customer in November paying $1,000/mo, they contribute $12,000 to ARR even though they've only paid $2,000 so far.
Why it matters: Investors and buyers think in ARR. Most SaaS valuations are expressed as a multiple of ARR (e.g., "10x ARR"). ARR milestones ($10K, $100K, $1M) are the shorthand for company stage.
Churn Rate
What it is: The rate at which you're losing customers or revenue.
Customer churn rate:
Customers who cancelled ÷ Total customers at start of period × 100
If you started the month with 100 customers and 5 cancelled, your monthly customer churn rate is 5%.
MRR churn rate (more important):
Churned MRR ÷ MRR at start of period × 100
5 customers cancelled, but they were paying $20/mo each. Churned MRR = $100. If starting MRR was $10,000, MRR churn rate = 1%.
Why MRR churn is more meaningful: Losing 5 customers paying $20/mo is very different from losing 5 customers paying $500/mo. Customer churn rate treats them the same; MRR churn rate does not.
Benchmarks:
- Under 2% monthly: healthy for SMB-focused SaaS
- 2-3%: acceptable, worth working on
- Over 5%: indicates a product or ICP problem
Annual churn calculation: Monthly churn rate does not simply multiply by 12. A 2% monthly churn rate = approximately 21% annual churn. Use the formula: 1 - (1 - monthly churn rate)^12.
LTV — Customer Lifetime Value
What it is: The total revenue a customer generates over their entire relationship with your product.
Simple calculation:
LTV = Average MRR per customer ÷ Monthly churn rate
If the average customer pays $100/mo and your monthly churn rate is 2%: LTV = $100 ÷ 0.02 = $5,000
More precise calculation:
LTV = ARPU × Gross Margin % × (1 ÷ Monthly churn rate)
Including gross margin makes LTV reflect actual profit, not just revenue.
Why it matters: LTV tells you how much you can spend to acquire a customer and still be profitable. The LTV:CAC ratio (covered below) is the key health metric this enables.
CAC — Customer Acquisition Cost
What it is: How much it costs to acquire a single paying customer.
How to calculate it:
CAC = Total sales and marketing spend ÷ Number of new customers acquired
If you spent $5,000 on marketing and sales in January and acquired 20 new customers, your CAC is $250.
Blended vs. channel CAC:
- Blended CAC: All acquisition spend ÷ all new customers (the simple number)
- Channel CAC: Acquisition spend per channel ÷ customers from that channel (tells you which channels are efficient)
Payback period: How many months of customer revenue it takes to recover the CAC.
Payback period = CAC ÷ Average MRR per customer
If CAC is $500 and average MRR is $100, payback period is 5 months.
Payback period benchmarks:
- Under 12 months: strong
- 12-18 months: acceptable
- Over 24 months: requires significant capital to fund growth
LTV:CAC Ratio
What it is: The relationship between what a customer is worth and what it costs to acquire them. The single most important ratio for SaaS unit economics.
Calculation:
LTV:CAC = LTV ÷ CAC
If LTV is $5,000 and CAC is $500, LTV:CAC = 10:1
Benchmarks:
- 3:1 or better: healthy business model
- Under 1:1: you're losing money on every customer — unsustainable
- Above 5:1: strong unit economics; you may be underinvesting in acquisition
NRR — Net Revenue Retention
What it is: The percentage of last period's revenue retained this period, accounting for upgrades, downgrades, and churn — but excluding new customer revenue.
How to calculate it:
NRR = (Starting MRR + Expansion MRR - Churned MRR - Contraction MRR) ÷ Starting MRR × 100
Example:
- Starting MRR from existing customers: $100,000
- Expansion (upgrades): +$10,000
- Churned MRR: -$5,000
- Contraction: -$2,000
- Ending MRR from same cohort: $103,000
NRR = $103,000 ÷ $100,000 = 103%
Why 100% NRR is a critical threshold:
- NRR above 100% (net negative churn): your existing customers grow revenue faster than churned customers shrink it. Your MRR grows even if you acquire zero new customers.
- NRR below 100% (net positive churn): your existing revenue base is shrinking. Acquisition must outrun this decline or revenue falls.
Benchmarks:
- 110%+ NRR: exceptional (rare, usually enterprise with strong expansion)
- 100-110% NRR: strong
- 90-100% NRR: acceptable
- Under 90%: a retention problem that acquisition cannot solve
ARPU — Average Revenue Per User
What it is: Average MRR per paying customer.
Calculation:
ARPU = Total MRR ÷ Total paying customers
Why it matters: ARPU tells you which segment of your customer base generates the most revenue and how your pricing compares to market. A rising ARPU over time (as you optimize pricing and upsell existing customers) is a healthy signal.
Quick reference table
| Metric | Formula | Good benchmark |
|---|---|---|
| MRR | Sum of monthly subscriptions | Growing month-over-month |
| ARR | MRR × 12 | — |
| Monthly churn | Churned MRR ÷ Starting MRR | Under 2% |
| LTV | ARPU ÷ Monthly churn rate | 3× CAC or more |
| CAC | Sales + marketing spend ÷ new customers | Payback under 12 months |
| LTV:CAC | LTV ÷ CAC | 3:1 or better |
| NRR | (Start + Expansion - Churn - Contraction) ÷ Start | Above 100% |
Frequently Asked Questions
When should I start tracking these metrics?
MRR from day one (or from your first paying customer). Churn once you have 20+ customers. LTV and CAC once you have 3+ months of data and a meaningful acquisition spend. NRR once you have a customer base large enough to have meaningful expansion and contraction.
What's the difference between gross churn and net churn?
Gross churn is just revenue lost from cancellations and downgrades. Net churn (= inverse of NRR) accounts for expansion — if new upgrades from existing customers more than offset cancellations, net churn is negative (which is excellent).
Can I use these metrics for a freemium product?
Yes, but track only paying customers in MRR, LTV, CAC, and churn calculations. Free users are not revenue. Track free-to-paid conversion rate separately as a leading indicator of pipeline health.
What's a good MRR growth rate?
For early-stage SaaS (under $10K MRR): 20-30% month-over-month is strong. This is the "triple, triple, double, double, double" (T2D3) growth path in compressed early form. Growth rates slow as the base grows — 5-10% monthly is strong at $100K+ MRR.
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