I used one Excel function to forecast months of revenue from my existing sales
https://www.makeuseof.com/excel-trend-function-to-forecast-revenue/
Forecast revenue with Excel’s TREND function
One formula is all it takes to project months of future sales
Common TREND function mistakes
If your forecast looks off, one of these issues could be to blame
When to use Excel’s TREND function
Your revenue might need more than a straight-line forecast
TREND function | Microsoft Support
https://support.microsoft.com/en-us/excel/functions/trend-function
TREND, functie | Microsoft Support
https://support.microsoft.com/nl-nl/excel/functions/trend-function