Forecasted Revenue Calculator

Forecast monthly business revenue over a set period using a growth rate

This forecasted revenue calculator is built for one practical job: turning a current monthly revenue figure and a single expected monthly growth rate into a simple forward-looking revenue forecast. If you are doing basic planning (staffing, marketing budget, inventory, runway, or target-setting), you usually do not need a full financial model to get a defensible starting point. You need an estimate that is consistent, repeatable, and clear about its assumptions.

The calculator treats your revenue as a monthly figure and applies the same growth rate each month over the forecast length you choose. It then totals up all months in the forecast window to show the total forecasted revenue for that period. You also get the ending-month revenue (what your monthly revenue would be at the end of the forecast), plus a simple snapshot of early months versus the last month. This makes it easier to sanity-check the trajectory instead of trusting a single number.

If you have a known planned change that will permanently lift (or reduce) revenue from a certain month onward, you can optionally add a one-time step change. This is useful for common situations like a price change, a new contract starting, a product launch, or the loss of a major client. The step change does not replace the growth rate. It applies an additional adjustment starting at the month you specify and carries forward through the remaining months.

Assumptions and how to use this calculator

• The forecast assumes a constant monthly growth rate across the entire period, unless you add an optional step change.
• The starting monthly revenue should represent a typical month (not an unusually high or low month) if you want a stable forecast.
• The step change is treated as a permanent level shift from the specified month onward (not a one-month spike).
• The forecast is revenue-only and ignores costs, cash timing, margins, taxes, and payment delays (it is not cash flow).
• Use modest growth rates for planning; very high percentages can produce unrealistic results quickly over longer horizons.

Common questions

What should I enter as “starting monthly revenue”?

Use the most recent normal month, or better, an average of the last 3 to 6 months if your revenue fluctuates. If you only have annual revenue, divide by 12 as a rough starting point, then treat the result as an estimate.

Can I use a negative growth rate?

Yes. A negative monthly growth rate represents decline. For example, -2% means each month is 2% lower than the prior month (before any optional step change). If you are in a seasonal business, a single negative rate is a simplification, so use it only for short planning windows.

How is total forecasted revenue calculated?

The calculator compounds your monthly revenue using the growth rate, month by month, and then adds up the revenue across all months in the forecast window. This produces a period total that matches the path implied by the growth assumption.

When should I use the one-time step change?

Use it when you expect a permanent change that starts in a specific month, such as a contract going live, a price increase, or a recurring service being cancelled. If the impact is truly temporary (one month only), leave the step change blank and treat the spike separately in your planning.

What is a sensible forecast length?

For most small and mid-sized businesses, 6 to 12 months is the sweet spot for this type of simple forecasting. Longer horizons magnify small assumption errors. If you need multiple phases of growth or seasonality, you need a different tool and a more detailed model.