# SaaS Unit Economics Explained: CAC, LTV and Payback for Indian Founders

Every serious investor conversation about your SaaS eventually lands on three letters: CAC, LTV, and payback. Here's what they mean, how to compute them honestly, and what "good" looks like for Indian B2B SaaS.

Customer Acquisition Cost (CAC)

Formula: total sales & marketing spend in a period ÷ new customers acquired in that period.

If you spent ₹15 lakh last quarter on salaries, ads, and tools and closed 30 customers, blended CAC = ₹50,000.

Two refinements that matter:

  • Paid CAC excludes organic signups — it shows whether paid channels work at all.
  • Segmented CAC by channel and customer size. Your enterprise CAC (₹3–5 lakh is common in India) and SMB CAC (₹10–40k) are different businesses; averaging them hides the truth.

Lifetime Value (LTV)

Simple formula: ARPA × gross margin % ÷ monthly churn rate.

Example: average revenue per account ₹25,000/month, 80% gross margin, 2% monthly churn:

LTV = ₹25,000 × 0.8 ÷ 0.02 = ₹10 lakh

Be honest about churn. Indian SMB churn often runs higher than founders admit; a cohort chart beats a hopeful percentage every time.

The LTV:CAC Ratio

The classic benchmark is 3:1. Below 1:1 you lose money on every customer. Above 5:1 usually means you're underinvesting in growth — competitors will eat the demand you're leaving on the table.

But context matters: enterprise deals with 18-month sales cycles can justify higher ratios because capital cycles slowly; high-churn SMB products need more.

CAC Payback Period

Arguably the most important number: months of gross profit needed to recover CAC.

Formula: CAC ÷ (ARPA × gross margin %).

₹50,000 CAC ÷ (₹25,000 × 0.8) = 2.5 months? That's exceptional. Under 12 months is healthy for Indian B2B SaaS; beyond 24 months means growth consumes cash faster than it returns.

Payback interacts powerfully with payment terms. A customer who prepays annually gives you the full year's cash on day one — instant payback. A customer insisting on monthly instalments delays recovery month by month. This is why payment terms are a unit-economics decision, not just an admin one; tools like KredFlow let you keep upfront collection even when buyers want instalments, protecting payback math.

Worked Example: Two Indian Startups

Startup A (SMB focus): CAC ₹30,000, ARPA ₹8,000/month, GM 75%, churn 3%/month.

LTV = ₹8,000 × 0.75 ÷ 0.03 = ₹2 lakh → LTV:CAC ≈ 6.7:1, payback = 5 months. Great economics, but churn caps durability.

Startup B (enterprise): CAC ₹6 lakh, ACV ₹20 lakh, GM 80%, churn 10%/year.

LTV = ₹16 lakh ÷ 0.10 = ₹1.6 crore → LTV:CAC ≈ 2.7:1, payback = 4.5 months. Lower ratio, but far stickier revenue.

Both are fundable. The lesson: ratios only make sense alongside churn, contract length, and cash timing.

How to Improve Each Lever

  • Lower CAC: founder-led sales before paid spend; double down on channels with proven conversion; shorten sales cycles (fewer touches per rupee).
  • Raise LTV: reduce churn with onboarding rigour; expand accounts with add-ons and seat growth; move upmarket gradually.
  • Speed payback: annual prepay incentives, usage-based expansion, disciplined discounting.

Track Them Monthly

Build a simple dashboard: blended and segmented CAC, LTV by cohort, payback by channel. Trends matter more than snapshots — a payback stretching from 9 to 14 months over two quarters is an early warning no pitch deck will show you.

Unit economics won't grow your company for you, but they tell you which growth is real. Master them early, and every later decision — hiring, pricing, fundraising — gets easier.

Common Traps in the Math

Watch for these silent distortions:

  • Excluding founder sales time from CAC. Your hours aren't free; cost them at market rate or early ratios flatter you.
  • Using signups, not activated customers, in the CAC denominator.
  • Gross margin computed on hosting alone, ignoring support salaries and third-party licences.
  • Churn measured on logos, not revenue. A ₹5 lakh logo churning hurts differently than a ₹20,000 one — track both.
  • Ignoring payment timing. Two customers with identical LTV differ enormously if one prepays annually and the other pays late monthly instalments; your payback period should reflect actual collection dates, not invoice dates.

Clean inputs beat sophisticated models. A simple spreadsheet with honest numbers updated monthly will outperform any dashboard built on optimistic defaults.