This calculator shows how a purchase today can effect your retirement. An example of this would be "smoking". Take what a pack of butts costs times 30 days and then input that number into the "dollar amount. Put in a small interest rate like you might find in a CD such as 4.5%. Then put in say 20 years. Hit calculate and be prepared to quit smoking. That is what one month of smoking does to you financially. For an even better effect take the monthly number and muliply it by 12 to get the effect of one year of smoking!
Another way to use this is to put in a big ticket item, such as a boat and see how that money would be effected.