doomath Calculator
SaaS MRR, Churn & Runway Calculator
Model SaaS unit economics including MRR, ARR, customer churn rate, customer lifetime value (LTV) and CAC payback period.
InputsChange a value to recalculate instantly
ResultUpdates as you type
FORMULA & STEPSSaaS MRR, Churn & Runway Calculator — Mathematical Derivation & Steps
3 StepsSequential Calculation Breakdown
1
Recurring Revenue Foundation
Total contracted recurring monthly and annualized baseline.
2
Customer Lifetime Value (LTV)
Expected gross margin contribution generated across customer lifespan.
3
Unit Acquisition Health (LTV : CAC)
Exceeds standard 3.0x healthy venture benchmark.
λ DooMathWork with this calculation
Local · deterministic · optionalQuick mathNatural-language-style shortcuts for deterministic arithmetic.
Calculator guide
How to use the SaaS MRR, Churn & Runway Calculator
Model SaaS unit economics including MRR, ARR, customer churn rate, customer lifetime value (LTV) and CAC payback period.
01Set inputsChoose values, units and assumptions.
02Apply the modelARR = MRR × 12; LTV = ARPU × Gross Margin% ÷ Churn Rate; CAC Payback = CAC ÷ (ARPU × Gross Margin%)
03Read the resultCheck the output against the assumptions before using it.
What this calculator does
Input your subscription customer base, average revenue per user (ARPU), customer churn rate and customer acquisition cost (CAC). The model evaluates SaaS health metrics.
Formula & method
ARR = MRR × 12; LTV = ARPU × Gross Margin% ÷ Churn Rate; CAC Payback = CAC ÷ (ARPU × Gross Margin%)
Assumptions & notes
- Gross margin percentage accounts for direct hosting and payment delivery costs.
- Healthy benchmark for LTV:CAC ratio is generally considered 3:1 or higher.
- Runway assumes current net monthly burn remains constant.