I use 2 very simple methods to get a hint on where my net worth will be in X years:

1. Take a simple savings rate calculator and add:
   1. actual net worth as starting point
   2. monthly saving amount
   3. period
   4. yearly yield (I only use 4% which is considered on the safer side if the money in invested in a world portfolio)

2. Use google spreadsheets and use the trend-option in graphs. It will adapt after every new entry and show you very nicely where you should land. It is preconfigured in my personal FIRE template you can use for free: