It's good to see that people are thinking about retirement $$$'s. I have done 20% since I was 23, and have never been sorry.
Briefly, using the calculator that Mwilding uses, a 20 year old, starting with $0, but contributing $8K/year would end up with $1,050,586.34 at age 50. This is assuming 2.2% inflation/year and 11% annual gain/year.
As pointed out...the key is to start young. Myself, I am not counting on any social security money. Any social security money will just be gravy.
The sad thing, where I work, I doubt if 20% of the people contribute the full 20% per year....heck, I bet only 50% contribute the 6% that is matched $1 for $1. IME, by starting with 20% after I got out of college, it was money I never saw, and have never missed.
An easy to swallow way to increase your percentage is to increase it every time you get a raise. If you get a 6% raise, give half to yourself, and increase your contribution by the remainder...or, increase it by the total of your raise. This way, you never miss the $$$'s.
Preach the value of retirement accounts to your coworkers. If they don't save, we'll be supporting them.
--Randy