Lifetime Value (LTV) vs LTV:CAC Ratio

Definition

Lifetime Value is the total revenue you can expect from a single customer over the entire duration of your relationship. It is the most critical number for understanding how much you can afford to spend on acquiring customers. The simplest formula: LTV = ARPU ÷ Monthly Churn Rate. A customer paying $100/month with 5% monthly churn has an LTV of $2,000. Netflix's LTV exceeds $1,200 per subscriber because churn is below 2.5% — this justifies their $17B+ annual content spend. LTV is the roof of your building: it determines the maximum CAC you can afford, the features you can build, and the team you can hire.

Common trap

Most founders massively overestimate LTV by assuming customers will stay forever. In reality, early-stage startups have limited cohort data. A startup with 6 months of history claiming $3,000 LTV is extrapolating a trend that hasn't been validated. Use conservative estimates (12-24 months cap) until you have 3+ cohorts with 12+ months of data. Also, LTV should be calculated on gross margin, not revenue — a $2,000 LTV with 50% gross margin means only $1,000 in actual profit to cover acquisition costs.

Practical use

Calculate LTV two ways: (1) Simple: ARPU ÷ Monthly Churn Rate. (2) Cohort-based: track actual revenue from each monthly cohort over time. Compare them — if your cohort LTV is lower than your formula LTV, your churn rate is misleading you (possibly due to early-life churn spikes). Always report Gross Margin-adjusted LTV: LTV × Gross Margin. This is the number that matters for unit economics.

Formula

Definition

The LTV:CAC ratio compares how much a customer is worth over their lifetime to how much it costs to acquire them. It is the single most important ratio for determining whether your business model is fundamentally viable. The golden benchmark is 3:1 — each customer generates 3x what you spent to acquire them. Below 1:1, you're paying more to acquire customers than they'll ever generate. Between 1:1 and 3:1, you're viable but thin. Above 5:1, you may be under-investing in growth — competitors who spend more can outpace you.

Common trap

The trap is looking at LTV:CAC in isolation without considering payback period. A 4:1 ratio with 24-month payback is actually worse than a 3:1 ratio with 6-month payback because you tie up cash for 2 years before seeing returns. Also, many companies inflate LTV:CAC by using revenue-based LTV instead of gross-margin-adjusted LTV. If your gross margin is 60%, your true economic LTV is only 60% of revenue LTV — cut your ratio by 40%.

Practical use

Calculate gross-margin-adjusted LTV:CAC ratio: (LTV × Gross Margin) ÷ CAC. If the result is below 3:1, you have two levers: increase LTV (reduce churn, add upsells) or decrease CAC (better targeting, organic channels). Also calculate by segment and channel — your enterprise LTV:CAC might be 5:1 while SMB is 1.5:1, meaning you should focus enterprise acquisition.

Formula