Should we include stock-based compensation in CAC?

Most rigorous LTV:CAC calculations use fully-loaded CAC including SBC for sales and marketing headcount. Excluding SBC understates real unit-economics cost. Ask any company reporting extraordinary ratios whether they include SBC — the honest ones will.

How do we handle CAC when we're doing lots of brand or product-led marketing?

This is genuinely hard. Pure brand spend and PLG investments produce customers indirectly and with long lag. Some companies split marketing spend into 'direct-response' (fully attributed to CAC) and 'brand/PLG' (treated as investment amortized over time). Whatever choice, be consistent and disclose the method.

What if we have negative churn?

Negative net churn (NRR > 100%) means LTV grows over time. Discount aggressively and cap the projection at 5-7 years — 'perpetual' negative churn assumptions inflate LTV to fantasy numbers.

LTV:CAC Ratio: Correct Definitions, Common Errors, and Real

The LTV:CAC ratio is the most misused metric in SaaS. Wrong-definition versions produce nonsense that ignores gross margin, discount rates.

LTV:CAC Ratio: What 3:1 Actually Requires and Why Most Companies Get It Wrong

LTV:CAC is treated as the fundamental SaaS unit-economics check, and the '3:1 is healthy' rule of thumb gets quoted in nearly every pitch deck. The problem: the version of LTV most decks use — ARPU divided by monthly churn rate, multiplied by a comfortable gross margin — is materially wrong for most businesses. It ignores retention curves that decay non-linearly, ignores the time value of money, and often applies a gross margin that overstates unit contribution. Correct LTV:CAC is more work to compute and produces less flattering numbers, but it's the version that actually predicts business health.

The formula, done properly

LTV = sum over time of (gross margin × ARPU × survival probability × discount factor). Not 'ARPU / churn rate.' The simplified formula only works if churn is perfectly constant and you don't discount future cash flows — neither of which is true. Correct version: build a cohort survival curve from actual data, apply gross margin (net of hosting, support, payment processing), discount future periods by ~10-15% (your cost of capital), and sum. Fully-loaded CAC = all sales and marketing spend in the period ÷ new customers acquired in the same period. Payback period matters as much as ratio.

The '3:1 rule' and its limits

The commonly-cited benchmark: LTV:CAC of 3 or higher means efficient unit economics; below 1 means you lose money on every customer. This is directionally right but requires unpacking. A 3:1 ratio with 30-month CAC payback means the LTV is realized very slowly — you tie up capital for 2.5 years per customer, which is fine at scale but painful for cash-constrained companies. A 3:1 ratio with 12-month payback is much healthier. Never look at the ratio without looking at the payback.

Common mistakes that inflate LTV

(1) Using revenue instead of gross-margin dollars — inflates LTV by whatever your COGS is. (2) Using aggregate churn rate rather than segment-specific rates — hides that small customers churn 3x faster than large ones. (3) Assuming churn stays constant forever — most cohorts churn faster in year 1 than year 3, so simplified LTV formulas that project forever off high early churn understate LTV; those that project off late-year low churn overstate it. (4) Ignoring the time value of money — a dollar in year 5 isn't worth a dollar today. (5) Adding aggressive expansion to LTV without accounting for the CS/expansion cost to earn it.

Segment the analysis

LTV:CAC by segment tells the actionable story. SMB segment: LTV $2K, CAC $800, ratio 2.5, payback 14 months. Mid-market segment: LTV $30K, CAC $8K, ratio 3.75, payback 10 months. Enterprise: LTV $250K, CAC $60K, ratio 4.2, payback 8 months. This might tell you: shift acquisition spend toward mid-market and enterprise, either fix SMB unit economics or exit that segment. Aggregate LTV:CAC hides these decisions. Every SaaS company past $5M ARR should compute segmented unit economics.

What good and great look like

Good: LTV:CAC ≥ 3, CAC payback ≤ 18 months, ratio stable or improving over time, expansion revenue contributing meaningfully to LTV. Great: LTV:CAC ≥ 4, CAC payback ≤ 12 months, NRR above 110% (which pushes LTV upward naturally over time), unit economics improving as you scale. Concerning: LTV:CAC below 2, or payback over 24 months, or ratio degrading as you scale (usually a sign that early adopters had unusually strong economics that don't generalize).

Frequently asked questions

Should we include stock-based compensation in CAC?: Most rigorous LTV:CAC calculations use fully-loaded CAC including SBC for sales and marketing headcount. Excluding SBC understates real unit-economics cost. Ask any company reporting extraordinary ratios whether they include SBC — the honest ones will.
How do we handle CAC when we're doing lots of brand or product-led marketing?: This is genuinely hard. Pure brand spend and PLG investments produce customers indirectly and with long lag. Some companies split marketing spend into 'direct-response' (fully attributed to CAC) and 'brand/PLG' (treated as investment amortized over time). Whatever choice, be consistent and disclose the method.
What if we have negative churn?: Negative net churn (NRR > 100%) means LTV grows over time. Discount aggressively and cap the projection at 5-7 years — 'perpetual' negative churn assumptions inflate LTV to fantasy numbers.