Analyze SaaS unit economics

Direct answer

For this review, define CAC, LTV, payback, LTV:CAC, contribution margin, and burn multiple as one system.

Why this question comes up

Founders need to know whether growth creates value or burns cash faster. This guide turns that concern into a review that can be repeated with a defined period, consistent inputs, and a visible trail back to the records.

Records to gather

• Revenue by customer and cohort, by month
• Gross margin, with hosting, support, and customer-success costs allocated
• Sales and marketing spend by period, including salaries and commission
• New customer counts by month, tied to the spend that produced them
• Churn and expansion by cohort, in both customer count and revenue

Review workflow

1. Define CAC before calculating it. Fully loaded — including sales salaries, commissions, and marketing headcount — or paid-media only? Both are used; they differ by multiples. State which.
2. Use gross margin, not revenue, for LTV. Lifetime value on revenue ignores the cost of serving the customer and inflates the ratio, often substantially.
3. Work in cohorts, not averages. A blended retention number mixes a strong 2024 cohort with a weak 2026 one and hides the trend that matters.
4. Separate gross and net revenue retention. Gross retention cannot exceed 100% and shows churn honestly. Net includes expansion and can mask a real churn problem behind upsell.
5. Compute CAC payback in months. For most operators this is more actionable than the LTV:CAC ratio, because it is a cash question rather than a lifetime estimate.
6. Attribute spend to the right period. Marketing spent in Q1 often produces customers in Q2. Matching them in the same period distorts CAC in both.

What a useful answer should include

• CAC with its definition stated, and the components included
• LTV calculated on gross margin, with the retention assumption made explicit
• Cohort retention curves rather than a blended average
• Gross and net revenue retention reported separately
• CAC payback in months alongside any LTV:CAC ratio
• The lag assumption between spend and customer acquisition

Common failure modes

• Revenue-based LTV. Ignoring cost of service can overstate LTV several-fold, which then flatters every ratio built on it.
• Blended retention. Averaging cohorts hides deterioration until it is a year old.
• Net retention as the headline. Expansion from a handful of large accounts can hold net retention above 100% while the majority of customers are leaving.
• Same-period CAC. Dividing this month’s spend by this month’s new customers ignores the sales cycle and produces a number that swings without meaning.
• Treating a benchmark as a target. Published SaaS benchmarks come from different stages, models, and segments. They are context, not a goal.

Community context

The linked community posts show why people search for this topic and which parts create confusion in practice. They are anecdotal. Use the reference sources and your organization’s policies for accounting treatment, tax, compliance, and final decisions.