8% is very generous, I thought 7% was the commonly used figure which gets you 800k in 40 years. When you acount for inflation that is not anything you should consider retiring on.
I can't believe people on a forum such as this are completely financially illiterate. The 7% rate is already inflation adjusted. The nominal rate is about 10%. So plug in a 7% real return. The result will be in 2015 dollars.
Your comment would've conveyed the same information had you omitted the first sentence.