How to build a 3-year financial projection for a startup

Build defensible 3-year revenue, cost, and cash projections in a single Google Sheet — the kind of model investors actually trust.

10 min read intermediateUpdated Jun 10, 2026
BI
Reviewed by the editorial team · Jun 10, 2026
Before you start
  • A pricing model (subscription, transactional, one-off)
  • A guess at unit economics — CAC, churn, gross margin

Step by step

  1. 01

    Start from the bottom up

    Never project '$10M revenue year 3 because the market is $1B'. Start from inputs: new customers per month × ARPU × retention = revenue. Top-down projections kill credibility.

  2. 02

    Build the revenue tab

    Columns: months 1-36. Rows: new customers, churn %, active customers, ARPU, MRR, ARR. Use formulas — never hardcode totals.

  3. 03

    Add the cost tab

    Two sections: COGS (hosting, payment processing, support — scales with revenue) and OpEx (salaries, rent, software — mostly fixed). Salaries are usually 60-70% of OpEx.

  4. 04

    Build the cash flow tab

    Opening balance + revenue collected − costs paid = closing balance. This is what tells you when you run out of money — the single most important number in a pitch.

  5. 05

    Add scenarios

    Duplicate the model. Base case, bull case (+30% growth), bear case (-30%). Investors ALWAYS ask 'what if you grow half as fast?'

  6. 06

    Sanity-check the unit economics

    LTV ≥ 3× CAC and payback period under 12 months are the rough investor benchmarks for SaaS. If yours don't, change the model — not the spreadsheet.

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