Here's the formula I'm working with for forecasting my 401k:
where t is in years, P(0) denotes starting principal, r denotes average annual rate of return, and c_i denotes biweekly contributions I make to the 401k (indexed by i because I could imagine a world where my contributions increase as I get older/paid more hopefully).
Example: Suppose I start with 75k already saved up and contribute 1k biweekly, then if we have a strong(ish) bull market w/ 10% average returns (pretend for a second), then I end up with approximately 620k after 10 years.
Question: Does this make sense or is it overly optimistic? I wonder how other people forecast their rate of return and if the yearly to monthly conversion makes sense or not for the 401k calculation w/o adding any stochastic elements.