SaaS & Subscription Metrics: MRR, Churn, NRR & Cohorts

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Tag every account's MRR change as new, expansion, contraction or churn, add the movements up into an MRR bridge and draw it as a waterfall chart.
• Turn a billing list with monthly and annual invoices into clean MRR, then summarise MRR, ARR, ARPA and the revenue mix by plan.
• Measure churn twice – by customers and by MRR – for six months, pool the rates correctly and annualise them without the ×12 mistake.
• Measure how much of last year's MRR the same accounts still pay today – with expansion (NRR) and without it (GRR) – and keep new customers out of the cohort.
• Turn a triangle of cohort MRR into % of starting MRR, build the weighted retention curve, find the best cohort and chart the curve.
• Add up every sales and marketing cost, divide by new customers for the fully loaded CAC per quarter and for the year, and work out how many months of gross profit it takes to earn it back.
• Calculate a conservative LTV for three customer segments – gross margin in, lifetime capped – compare it with CAC and work out the most you can spend to win a customer.
• Score a year of growth on three investor metrics: how much cash each new dollar of ARR costs, how much MRR comes in per dollar that leaves, and whether growth plus margin reach 40%.