How to Build a 90-Day Cash Flow Forecast for Your SaaS
Most SaaS founders discover they're running out of money 30 days too late. A 90-day cash flow forecast gives you the foresight to act before a crisis — not during one. Here's how to build one that actually works.
Why Spreadsheets Fail at Forecasting
Spreadsheets give you one number: a single best-guess. But the future isn't a single number — it's a range of possibilities.
What you actually need are confidence bands:
- P50 (Most Likely): 50% chance cash stays above this level
- P80 (Optimistic): 80% chance cash stays above this level
- P95 (Conservative): 95% chance cash stays above this level
Spreadsheets can't calculate these automatically. They require statistical modeling based on your historical churn, growth rate, and revenue variance.
The 4 Inputs You Need
Current MRR
Your baseline. Every forecast starts from today's recurring revenue.
Monthly Churn Rate
The % of customers who cancel each month. Even 2% churn compounds dramatically over 90 days.
New Customer Growth Rate
How many new customers do you acquire per month on average? Use the last 3 months.
Fixed Monthly Expenses
Salaries, hosting, tools, subscriptions. These determine your burn rate.
Step-by-Step: Building Your 90-Day Forecast
Calculate your Net Revenue Retention (NRR)
If NRR > 100%, your existing customers are growing you. Under 100%, you're leaking.
Project MRR for each of the next 90 days
Use your growth rate and churn rate to project forward.
Subtract fixed expenses from projected MRR
Do this for each month to get net cash flow.
Run 3 scenarios using different churn assumptions
The standard deviation measures how much your churn varies month to month.
Sum the cumulative cash balance across all 90 days
If your P95 balance hits zero before day 90 — you have a runway problem.
What to Do With the Forecast
- If P95 runway < 60 days → cut non-essential expenses immediately
- If P50 runway < 90 days → accelerate acquisition or explore funding
- If P80 runway > 180 days → you have room to hire or invest in growth
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Get Your 90-Day Forecast Automatically
AI Finance Ops calculates P50/P80/P95 confidence bands from your Stripe data — no spreadsheets, no formulas, no guessing.
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