SaaS Unit Economics

Frequently Asked Questions

What are SaaS unit economics?

Per-customer profitability metrics: CAC, LTV, payback period, gross margin, contribution margin. Healthy: LTV:CAC 3:1+, CAC payback <12 months, gross margin >75%. Negative unit economics ("burn for growth") only works if you can prove improvement at scale.

How do I improve unit economics?

Reduce CAC (better targeting, organic channels), increase ARPU (move upmarket, add features), reduce churn (better onboarding, customer success), improve gross margin (infrastructure efficiency, automation). Each lever amplifies the others.

When should I optimize unit economics vs. growth?

Unit economics first if: capital is expensive, market is mature, or competitors are profitable. Growth first if: winner-take-all market, network effects, or you have abundant capital. Most companies eventually need both ("efficient growth" frontier).

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How This Calculator Works

This tool answers the make-or-break SaaS question: does one customer earn back more than it costs to acquire? From monthly price, gross margin, churn, and CAC it computes monthly gross profit (price × margin%), expected customer lifetime (100 ÷ churn%), LTV (monthly gross profit × lifetime months), CAC payback period (CAC ÷ monthly gross profit), and the headline LTV:CAC ratio. Unlike the ARR tool, which models aggregate revenue, this isolates the economics of a single customer cohort.

The Two Numbers Investors Check First

LTV:CAC ≥ 3:1 is the rule of thumb. Below 3 you are not extracting enough value per acquisition dollar; far above 5 you may be under-investing in growth and leaving the market to competitors.

CAC payback < 12 months for SMB, <18–24 for enterprise. Payback matters more than LTV:CAC for cash-constrained startups - a great LTV that takes 30 months to recoup still starves the business in the meantime.

The Margin Trap in LTV

LTV must be built on gross profit, never on revenue. Using revenue-based LTV is the most common way SaaS founders fool themselves: a $99 plan at 75% margin contributes $74/mo, not $99. At a 50% margin the same churn produces a third less LTV. Hosting, support, and payment fees all belong in the margin number - an optimistic margin inflates LTV and makes unprofitable acquisition look healthy.

Why the Lifetime Formula Is Fragile

Lifetime = 1 ÷ churn assumes a constant churn rate forever, which overstates LTV because real churn is highest early and survivors are stickier - but the simple model also ignores expansion revenue, which understates it. The bigger issue: at low churn the formula explodes (1% monthly churn implies a 100-month, ~8-year life). Cap modeled lifetime at 3–5 years for sanity; no forecast that far out is reliable.

Common Mistakes

Loaded vs blended CAC. CAC must include sales salaries, tools, and overhead - not just ad spend. Blended CAC (all sign-ups) flatters paid channels.

Mixing monthly and annual churn. 5% monthly ≈ 46% annual - the lifetime math is wildly different; match the period.

Ignoring expansion. Excluding upsell understates LTV for products with strong net retention.

Treating LTV:CAC as the only gate - a strong ratio with 30-month payback can still bankrupt a startup.

Frequently Asked Questions

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