Definition (canonical)
SaaS (Software as a Service) is a model where software runs centrally in the vendor's cloud and customers pay a recurring subscription for access — no installation, no license ownership, updates for everyone at once. As a business model it trades one-time license revenue for compounding recurring revenue.
The economic engine
Three properties power the model. Recurring revenue: each sale adds a layer that keeps paying — growth stacks instead of restarting every January (MRR/ARR capture this). Near-zero marginal cost: serving customer 1,001 costs little beyond infrastructure, so gross margins reach 70–85%. Compounding retention: with NRR above 100%, the existing base grows by itself and new sales ride on top. The same engine has a dark side: revenue arrives in monthly slices while acquisition costs land upfront — early-stage SaaS burns cash BY DESIGN, and misreading that as failure (or as license to burn) kills companies in both directions.
The metrics stack
SaaS is unusually measurable, and the canon is settled: MRR/ARR for scale; growth rate; churn and NRR for durability; CAC, LTV:CAC and payback for acquisition efficiency; gross margin for model integrity; burn multiple for capital discipline. Investors read them as one organism — spectacular growth with weak NRR prices like a leaky bucket; modest growth with 115% NRR prices like an annuity.
What makes SaaS hard
Not the software — the distribution and the durability. Competition is global by default; switching costs must be EARNED through integrations and workflow depth; a subscription is a promise renewed monthly, so product neglect converts to churn with a lag that flatters you until it doesn't. Pricing is a first-class product decision (per seat, per usage, tiered) revisited yearly. And the services trap looms: enterprise deals pull founders toward custom work that feels like revenue and quietly converts a product company into an agency (keep it out of ARR).
FAQ
SaaS vs cloud vs subscription? Cloud is the delivery infrastructure; subscription is the billing model; SaaS is the combination applied to software as a product.
What gross margin should SaaS have? Below ~70% investors read "services in disguise or infrastructure problem"; 75–85% is the healthy band.
Is SaaS still a good business to start? Category leaders are entrenched, but verticalization (SaaS for dental clinics, for freight brokers…) keeps opening defensible niches — distribution advantage decides.
Related: MRR & ARR · Subscription Model · Churn · Unit Economics Reviewed: 2026-07-15 · Sources: SaaS canon