Also, this article just uses the simplest of formulas and didn’t factor cost of living or salary growth into the equation. It’s interesting as a guideline but wouldn’t be realistic for long-term scenarios. For example, an eighteen year-old investor in 1953 hoping to accumulate $50,000 by the year 2013 would have contributed $5/month and finally reached the target this year (at the age of 78). Unfortunately, $50,000 doesn’t go very far any more, which would have seemed counter-intuitive to an investor in 1953 just as it’s counter-intuitive to a teenager today that $1,000,000 won’t buy very much in 2073 (the Yahoo article above shows that $100/month will allow you to reach $1 million by 2073, but it won’t be worth as much as you’d expect).

The key is that if you’re targeting a specific amount for a projected retirement that’s decades away then you don’t want to get too complacent. For example, investing $2,000/month now will allow you to reach $1 million around the year 2033, but it might not be enough to retire on. But don’t worry, your salary will also grow tremendously before you retire and your contributions will grow accordingly. So you’ll still meet your retirement goals, and do so with a much higher retirement stash than originally anticipated.

It’s probably best to use the targets in this article

http://www.mrmoneymustache.com/2012/01/13/the-shockingly-simple-math-behind-early-retirement/, which shows that saving a percentage of your salary will give you a very solid estimate of when you can retire without having to imagine or worry about how much inflation will erode your money over the decades to come.