[header] How to calculate future value [title] Understand how the value of money fluctuates over time. [step] The value of $100 is different today than it was five years ago or will be five years from now. When you invest money or deposit it into an interest-bearing account, the value will increase or decrease depending on the rate of return. 
In addition, inflation affects the value of money. Even though $100 may be enough to purchase an item today, it may not be enough to purchase that same item in the future.