SaaS Revenue Forecast Calculator

Project customers, MRR and cumulative revenue across a planning horizon.

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.

Worked scenario

Begin with current recurring revenue and model new, expansion, contraction and churn movements month by month. Use separate assumptions for committed backlog and uncommitted pipeline. Build base, downside and upside cases, and reconcile each completed month before extending the remaining forecast.

How to interpret the result

The forecast is most useful as a transparent driver model. A single growth percentage hides whether revenue depends on sales capacity, conversion, retention or expansion. Compare actual movement against each driver, not only total revenue, so forecast error changes the relevant operating assumption.

Input reference

Currency
Example default: USD
Starting customers
Example default: 250
New customers per month
Example default: 35
Monthly churn rate
Example default: 2%
Average revenue per account
Example default: 120
Forecast months
Example default: 12

Common mistakes

  • Applying one compound growth rate to every month.
  • Treating pipeline as contracted recurring revenue.
  • Ignoring capacity, seasonality and implementation delay.

Before using the result

  1. Forecast recurring movements as separate drivers.
  2. Maintain base, downside and upside assumptions.
  3. Reforecast after every closed reporting period.

Questions to check before deciding

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.

Detailed operating guide

SaaS forecasting and runway: drivers, scenarios and decision dates

A revenue forecast explains operating drivers; a runway plan explains cash timing. This guide connects them without treating an average burn rate as a complete plan.

Read the guide