Method and assumptions
This deterministic forecast is a scenario tool, not a statistical prediction. Run conservative, base and upside cases with separate assumptions.
Each month: ending customers = prior customers + new customers - prior customers × churn rate; MRR = ending customers × ARPA.
Common questions
Does this model expansion revenue?
No. Use a higher ARPA scenario or MRR model when expansion needs to be explicit.
How should seasonality be handled?
Run different new-customer assumptions by month in a spreadsheet when seasonality matters.
Independent planning calculator. Not financial, tax, legal or investment advice.