LTV vs CAC
Quick answer: LTV (lifetime value) and CAC (customer acquisition cost) aren't competing metrics — they're paired. The ratio LTV ÷ CAC tells you whether the business is sustainable; payback period tells you whether you can fund the wait. Healthy DTC: LTV:CAC ≥ 3:1 with payback under 12 months. Below either threshold, you're either unsustainable or cash-constrained.
| Criterion | LTV (Lifetime Value) | CAC (Acquisition Cost) |
|---|---|---|
| What it measures | Total revenue (or contribution) per customer over their relationship | Total spend ÷ new customers acquired |
| Time horizon | 12-36 months typical | Current period (monthly typical) |
| Inputs | AOV × purchase frequency × cohort lifespan × margin | Ad spend + agency + tools + content + team time |
| Direction over time | Should grow with retention improvements | Tends to grow with audience saturation |
| Healthy DTC level | $200-1,000+ (depends on category) | $30-150 (depends on AOV) |
| Healthy ratio | LTV ≥ 3× CAC | |
The 3:1 rule isn't arbitrary. The math: 1× covers customer acquisition. The next 1× covers fixed overhead (rent, salaries, software, taxes). The third 1× provides margin and reinvestment capacity. Below 3:1 you're break-even at best; below 1:1 you're losing money on every customer acquired (rare for established brands but common for new launches).
A business with LTV:CAC of 5:1 but 24-month payback can still go bankrupt. The 5:1 ratio is real, but the cash to fund 24 months of acquisition isn't. Payback period — months to recover CAC from customer revenue — is the cash discipline metric. Under 6 months: cash-friendly growth. 12-18 months: needs strong cash position. Above 18 months: rare for sustainable DTC.
Using revenue instead of contribution. $1,000 of LTV at 30% gross margin is $300 of contribution. Apply CAC to contribution, not revenue. The LTV:CAC ratio collapses substantially when calculated correctly.
Including refunds and chargebacks. If 10% of customers refund, your effective LTV is 90% of nominal LTV. Models that ignore refunds overstate LTV systematically.
Extrapolating from new cohorts. A 3-month-old cohort hasn't yet shown its retention curve. Modeling 24-month LTV from 3 months of data routinely overstates by 30-50%.
Using CPA instead of CAC. CPA from ad platforms is just the in-platform cost per conversion. CAC includes agency fees, content production, tooling, and team time. CAC is typically 1.3-1.8× the platform CPA.
Not separating new vs returning. If 40% of orders are returning customers, those don't count as new acquisitions. CAC is spend ÷ new customers, not spend ÷ all orders.