Core SaaS Metrics Explained
Average Revenue Per Account (ARPA) measures the monthly recurring income from a single customer. It reveals pricing power and usage patterns across your customer base. Calculate it by dividing total monthly recurring revenue by active customer count.
Gross Margin is the percentage of revenue remaining after direct costs (hosting, support, payment processing). A SaaS business with 70% gross margin retains $0.70 per dollar earned. This figure directly reduces lifetime value calculations because it reflects actual profitability.
Monthly Churn Rate is the percentage of customers who cancel each month. A 5% monthly churn means you lose one-twentieth of your customer base every 30 days. This rate compounds annually—5% monthly churn equals roughly 46% annual churn.
Monthly Recurring Revenue (MRR) is predictable monthly income from active subscriptions. Track it separately from one-time fees or variable usage charges to maintain clean unit economics.
Customer Lifetime Value Formula
The LTV calculation accounts for churn decay, account expansion, and profitability in a single metric. Divide your MRR by customer count if ARPA is unknown; the formula adapts automatically.
LTV = [0.5 × (1 ÷ churn) × (2 × ARPA + account_expansion × (1 ÷ churn − 1))] × gross_margin
ARPA— Average revenue per account per month (in currency units)churn— Monthly churn rate as a decimal (e.g., 0.05 for 5%)account_expansion— Average monthly fixed growth in MRR per account (e.g., $10/month)gross_margin— Gross margin as a decimal (e.g., 0.70 for 70%)
Calculating ARPA and MRR
You have two paths to input your revenue data. Direct entry: If you know your average revenue per account, enter it immediately. This applies to uniform pricing models where all plans cost the same or you've already computed a weighted average.
From total revenue: If MRR varies across customer segments or you only know total monthly revenue, divide total MRR by your active customer count. A company with $50,000 MRR and 100 customers has $500 ARPA. This method automatically populates ARPA when you toggle the "Calculate ARPA" option.
Track both figures monthly. As pricing or customer mix shifts, ARPA changes. Account expansion models (where customers upgrade mid-contract) increase ARPA over time and boost LTV proportionally.
Impact of Churn on Lifetime Value
Churn is the primary lever affecting LTV. A business with 2% monthly churn (≈24% annual) generates far higher lifetime value than one with 5% monthly churn (≈46% annual), even with identical ARPA and margins. Mathematically, LTV increases exponentially as churn approaches zero because customers remain longer.
Reducing monthly churn from 5% to 3% can double LTV without raising prices. This is why retention improvements often deliver faster growth than acquisition spend. Common drivers of churn include product stagnation, poor onboarding, feature parity with competitors, and pricing misalignment. Monitor churn weekly and segment it by cohort, product tier, and geography to isolate causes.
Account expansion—such as cross-selling or usage-based pricing increases—offsets churn mathematically. A customer paying $500/month who expands to $600/month lengthens their virtual lifetime by absorbing early-stage churn losses.
Practical Considerations for LTV Planning
Apply these insights to avoid overestimating LTV or misdirecting acquisition budgets.
- Exclude one-time payments — LTV assumes predictable monthly revenue only. Exclude setup fees, onboarding charges, or custom implementation fees from ARPA. These inflate the figure and distort comparison between customers acquired at different times.
- Segment by acquisition channel — Customers acquired through partnerships often have lower churn than those from paid search. Calculate LTV separately by source to allocate acquisition spend efficiently. A channel with high LTV justifies higher CAC (customer acquisition cost) budgets.
- Update margins quarterly — Gross margin fluctuates with scale, infrastructure costs, and service portfolio changes. Use conservative estimates if your cost structure is new. Overestimating margins leads to overspending on acquisition relative to profitability.
- Account for expansion realistically — Not all customers expand. If only 20% of customers upgrade annually, don't assume 100% monthly account expansion. Model expansion conservatively or calculate LTV without it, then treat expansion revenue as incremental upside.