TL;DR

A financial model is not a prediction — it is a structured framework for thinking about your business. A good startup financial model is built from unit economics, shows the path to profitability, and is transparent about key assumptions.

The Building Blocks

Revenue Model (build bottom-up from unit economics):

For SaaS: New customers per month × ACV, monthly churn rate, expansion revenue

MRR = (Prior MRR + New MRR + Expansion MRR) - Churned MRR

Cost Model:

COGS: Hosting, customer support, implementation, third-party software

OpEx: Sales & Marketing (by channel), R&D (engineering headcount), G&A

Headcount Model:

  • Current headcount by department
  • Planned hires by quarter
  • Fully loaded cost per employee (salary + benefits + taxes + equity)

Cash Flow:

EBITDA - Capex ┬▒ Working capital changes = Free cash flow

Key Model Outputs

1. Monthly P&L (at least 24 months)

  1. Cash balance (showing when you run out of money)
  2. Key metrics dashboard (MRR, ARR, CAC, LTV, gross margin, burn rate, runway)

4. Scenario analysis (base, upside, downside)

Common Mistakes

1. Top-down revenue assumptions — "1% of a $10B market" is not a model

2. Ignoring COGS — gross margin matters

  1. Underestimating hiring timelines — 2–3 months to recruit, 3–6 months to ramp
  2. No scenario analysis — investors will stress-test your assumptions
  3. Circular references — use a separate assumptions tab

Key Takeaways

Key Takeaways
  • Build revenue from unit economics, not top-down market share assumptions.
  • Model headcount explicitly — it drives the majority of startup costs.
  • Show cash balance monthly — investors need to see when you run out of money.
  • Include scenario analysis (base, upside, downside).
  • A financial model demonstrates management quality — make it defensible.