Essence
Unit economics answers the core business question: do we earn more from one customer than we spend to acquire them? A "unit" = one customer. If a unit loses money, scaling just burns cash faster ("sell a ruble for 90 kopecks, make it up on volume" — you won't). So check the economics BEFORE ramping marketing.
Formulas
CAC = (marketing + sales) / customers acquired.
ARPU = revenue / users; ARPPU = revenue / PAYING users.
Churn = share lost per period; Retention = 1 − churn; lifetime (mo) = 1/churn.
LTV = ARPU × gross margin × (1/churn). MRR; ARR = MRR×12.
Payback (mo) = CAC / (ARPU × gross margin). LTV/CAC.
Health benchmarks
LTV/CAC ≥ 3 (healthy); payback < 12 mo; LTV/CAC < 1 = unit loses money; ≫ 5 = maybe under-investing in growth.
Worked example
Marketing+sales 300,000₽/mo; 150 paying acquired; price 1,000₽/mo; margin 80%; churn 5%.
CAC = 300,000/150 = 2,000₽. Lifetime = 1/0.05 = 20 mo. LTV = 1,000×0.8×20 = 16,000₽.
LTV/CAC = 16,000/2,000 = 8.0 (great). Payback = 2,000/(1,000×0.8) = 2.5 mo.
If churn → 15%: lifetime ≈ 6.7 mo, LTV ≈ 5,360₽, LTV/CAC ≈ 2.7 (below 3). LTV is very churn-sensitive — retention often beats acquisition.
When to use
Before scaling marketing; when choosing channels (compare CAC/payback); for product decisions (effect on churn/ARPU/LTV). Compute yours in the built-in unit-economics calculator.
Pitfalls
Forgetting gross margin; ARPU vs ARPPU; "make it up on volume" at LTV/CAC < 1; ignoring payback under cash crunch; constant churn (use cohorts).