What is LTV/CAC Ratio?
The LTV/CAC ratio compares customer lifetime value to the cost of acquiring that customer. Industry benchmarks: best-in-class SaaS targets 3:1 or higher; consumer subscription targets 4:1+; pure transactional commerce should also exceed 3:1. A ratio below 1 means you lose money on every customer — the firm is not viable. A ratio between 1 and 3 may be acceptable for short payback if churn is low and growth justifies investment. A ratio above 5 may suggest under-investment in growth. Payback period — the time to recover CAC through gross profit — is the complementary metric; SaaS targets 12-18 month payback. The LTV/CAC discipline forces honest evaluation of growth quality.
How LTV/CAC Ratio actually works
The framework breaks down into the following moving parts. Knowing what each piece is — and what it is not — is what separates a B-grade answer from an A-grade answer in a written assignment.
- LTV/CAC = Customer Lifetime Value / Customer Acquisition Cost
- SaaS benchmark: 3:1+
- Consumer subscription: 4:1+
- <1: model not viable
- 5+: may indicate under-investment
- Pair with payback period (months to recover CAC)
A worked example: Slack
Slack's LTV/CAC ratio at scale was approximately 5-6x — exceptional for SaaS. The firm benefited from product-led growth (low CAC because users invited colleagues), high retention (annual net revenue retention of 130%+), and high gross margins (80%+). The ratio supported Salesforce's $27B acquisition in 2021 — at that LTV/CAC, every dollar invested in growth produced $5-6 in customer value. Most SaaS firms struggle to maintain 3:1 as they scale because CAC rises faster than LTV. Slack's combination of viral growth and high retention is unusual; it is the operational signature of best-in-class product-led growth.
Don't lose marks for these
- Calculating LTV before retention curves stabilize
- Ignoring rising CAC over time
- Optimizing on growth without LTV/CAC
How to use this on the exam
Score-maximizing moves
- Cite industry benchmarks
- Pair with payback period
- Recognize ratio breakdowns at scale
When to use LTV/CAC Ratio (and when not to)
Use LTV/CAC Ratio when your assignment asks you to analyze, structure, or recommend — and when you have at least two data points to populate every cell of the framework. Skip it when the question is asking for a numerical answer or a single recommendation, since LTV/CAC Ratio is a structuring tool, not a calculator.