What it means
The commercial shift matters far more than the technical one. Selling a perpetual licence produces a large payment on day one, while selling a subscription produces a smaller payment every month, so revenue is recognised across the life of the contract rather than at signature.
That single change reshapes the whole business. Early years consume cash because the cost of winning a customer is paid up front while the revenue arrives slowly, which is why SaaS companies are judged on recurring revenue, retention and payback period rather than on one year's profit.
The core measures are monthly recurring revenue and its annualised version, churn, which is the percentage of customers or revenue lost each period, customer acquisition cost and customer lifetime value. Gross margins in the sector typically run somewhere between 70% and 85%, because hosting, support and customer success costs rise with usage even though the software itself is written once.
Contracts are commonly annual or monthly, priced per user, per unit of usage, or in tiered packages that bundle features. Expansion revenue from existing customers matters enormously, and a company whose existing base grows faster than it loses customers has net revenue retention above 100%.
The subscription label on its own does not make a business attractive. High churn turns recurring revenue into a leaking bucket, and heavy discounting to hit a growth number can push the payback period out past the point where an average customer ever repays what it cost to win them.
In practice
Real-world examples.
Example
An accountancy practice replaces its installed ledger software with a subscription platform at $65 per user per month for 40 users, costing $31,200 a year. It gives up ownership but removes server maintenance, version upgrades and the periodic five-figure upgrade payment it used to budget for.
Example
A field services provider prices by usage rather than seats, charging $1.20 per completed job logged. Revenue grows automatically as customers get busier, which smooths seasonality but makes forecasting harder than a fixed per-seat model.
Example
A human resources platform reports 118% net revenue retention. It loses about 8% of its customer base each year but existing customers add modules and headcount fast enough that revenue from the base still grows without any new logos.
Formula
Calculation
MRR = number of customers x average monthly revenue per customer
ARR = MRR x 12
Average customer lifetime in months = 1 / monthly churn rate
LTV = monthly revenue per customer x gross margin % x average lifetime in months
CAC payback in months = CAC / (monthly revenue per customer x gross margin %)
A scheduling software company has 1,200 customers each paying $400 a month, a gross margin of 80%, monthly churn of 2% and a customer acquisition cost of $4,000.
MRR = 1,200 x $400 = $480,000
ARR = $480,000 x 12 = $5,760,000
Average lifetime = 1 / 0.02 = 50 months
LTV = $400 x 0.80 x 50 = $16,000
LTV to CAC ratio = $16,000 / $4,000 = 4.0
CAC payback = $4,000 / ($400 x 0.80) = $4,000 / $320 = 12.5 months
Annual gross profit per customer = $400 x 12 x 0.80 = $3,840
Total annual gross profit = 1,200 x $3,840 = $4,608,000, which is 80% of the $5,760,000 ARR
Now suppose monthly churn doubles to 4% because a competitor launches a cheaper tier. Average lifetime halves to 25 months, LTV falls to $400 x 0.80 x 25 = $8,000, and the LTV to CAC ratio drops from 4.0 to 2.0. Nothing about the product or the sales team changed, yet the economics of every new customer just became half as attractive.Case study
Seen in the real world.
Marlowe Rota is an illustrative, fictional company selling shift scheduling software to hospitality groups. It reached $5,000,000 of annual recurring revenue in four years and its board was pleased with the growth rate until an investor asked a question nobody had modelled properly.
The analysis was uncomfortable. Marlowe's headline churn of 2% a month was an average across two very different groups: enterprise chains churning at well under 1% and independent single-site venues churning at nearly 5%. Independents accounted for 70% of new customers by count and their average lifetime was barely 20 months, well short of the roughly 14 months of gross profit needed to repay a $3,600 acquisition cost with any real margin left over.
Marlowe moved the majority of independent sales to a self-service sign-up with no sales commission, cutting acquisition cost for that segment to under $600, and redirected the field sales team entirely to multi-site groups. Headline growth slowed for two quarters and then recovered with far better unit economics. This fictional example illustrates a common trap: a blended average can hide a segment that is being sold at a loss.
Watch out
Common mistakes.
- Recognising a full annual subscription as revenue when the invoice is raised. The cash arrives up front but the revenue belongs to the months it covers, and the unearned portion sits on the balance sheet as deferred revenue.
- Calculating lifetime value from revenue rather than gross profit. Ignoring hosting and support costs overstates LTV by 20% to 30% in a typical business and makes weak acquisition spending look justified.
- Reading a single blended churn number as if the customer base were uniform. Averages routinely hide one segment retaining beautifully while another leaks badly, and the two need different strategies.
Questions
People also ask.
What is the difference between MRR and ARR?
MRR is the recurring revenue booked in a month and ARR is that figure annualised, so ARR is simply MRR multiplied by 12 rather than a separate measure of cash received.
What counts as a healthy LTV to CAC ratio?
Around 3.0 is widely treated as sound, since much below that suggests acquisition is too expensive while much above it can mean the business is under-investing in growth.
Is SaaS always cheaper than buying software outright?
Not over a long horizon, because subscriptions continue indefinitely, but the comparison should include the hardware, upgrades, downtime and internal support that a self-hosted licence quietly requires.
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