After doing some research, I noticed that Fidelity appears to have fund fees between 0.71% and 0.91%, whereas Vanguard has fund fees between 0.21% or 0.22%. How do I calculate the impact that these differences will have on my investments?
It's not all that complicated. You just subtract that from the real annual return each year. That is, if the fund goes up by 2% and has a .9% fee your real return is 1.1% instead of two.
Fees can take a real bite out of your investment. I like to think of it this way: You have no real control over the rate of return of a mutual fund, but you can control how much fee you are going to pay. So by selecting a fund with a 1% smaller fee you are automatically adding 1% to the return, it is one of the few guarantees you can get.
Studies have shown that managed funds do not do better than the index over the long term. So when one buys a managed fund that tracks itself against the S&P and tells me they are paying 1%/yr for the privilege, I tell them that my 401(k) S&P index charges me .05%, this is 1% over 20 years, total. The other person would lose 20% over that time.
It gets even crazier when you are retired and are trying to make your money last. You are taught that a 4% withdrawal rate is pretty safe, but you may be giving a full 1% to a fund manager off the top, good year or bad.