If you were offered $100 today or $100 a year from now, which would you choose? Would you rather have $100,000 today or $1,000 a month for the rest of your life?
Net present value (NPV) provides a simple way to answer these types of financial questions. This calculation compares the money received in the future to an amount of money received today, while accounting for time and interest. It's based on the principle of time value of money (TVM), which explains how time affects monetary value. (For background reading, see Understanding The Time Value Of Money.)
The TVM calculation may look complicated, but with some understanding of NPV and how the calculation works, along with its basic variations: present value and future value, we can start putting this formula to use in common application.
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Time Value of Money
If you were offered $100 today or $100 a year from now, which would be the better option and why?
This question is the classic method in which the TVM concept is taught in virtually every business school in America. The majority of people asked this question choose to take the money today. But why? What are the advantages and, more importantly, disadvantages of this decision?
There are three basic reasons to support the TVM theory. First, a dollar can be invested and earn interest over time, giving it potential earning power. Also, money is subject to inflation, eating away at the spending power of the currency over time, making it worth less in the future. Finally, there is always the risk of not actually receiving the dollar in the future  if you hold the dollar now, there is no risk of this happening. Getting an accurate estimate of this last risk isn't easy and, therefore, it's harder to use in a precise manner.
Illustrating the Net Present Value
Would you rather have $100,000 today or $1,000 a month for the rest of your life?
Most people have some vague idea of which they'd take, but a net present value calculation can tell you precisely which is better, from a financial standpoint, assuming you know how long you will live and what rate of interest you'd earn if you took the $100,000.
Specific variations of time value of money calculations are:
 Net Present Value (lets you value a stream of future payments into one lump sum today, as you see in many lottery payouts)
 Present Value (tells you the current worth of a future sum of money)
 Future Value (gives you the future value of cash that you have now)
Determining the Time Value of Your Money
Which would you prefer: $100,000 today or $120,000 a year from now?
The $100,000 is the "present value" and the $120,000 is the "future value" of your money. In this case, if the interest rate used in the calculation is 20%, there is no difference between the two.
Five Factors of a TVM Calculation.
1.Number of time periods involved (months, years)
2.Annual interest rate (or discount rate, depending on the calculation)
3.Present value (what do you have right now in your pocket)
4.Payments (if any exist. If not, payments equal zero)
5.Future value (the dollar amount you will receive in the future. A standard mortgage will have a zero future value, because it is paid off at the end of the term)
Many people use financial calculators to quickly solve these TVM questions. By knowing how to use one, you could easily calculate a present sum of money into a future one, or vice versa. The same goes for determining the payment on a mortgage, or how much interest is being charged on that shortterm Christmas expenses loan. With four of the five components inhand, the financial calculator can easily determine the missing factor. To calculate this by hand, the formulas for future value (FV) and present value (PV) would look like this:
FV = PV (1+i)^{N} 
PV = FV (1+i)^{N} 
Applying Net Present Value Calculations
Net present value calculations can also help you discover answers to other questions. Retirement planning needs can be determined on an overall, monthly or annual basis, as can the amount to contribute for college funds. By using a net present value calculation, you can find out how much you need to invest each month to achieve your goal. For example, in order to save $1 million dollars to retire in 20 years, assuming an annual return of 12.2%, you must save $984 per month. Try the calculation and test it for yourself. (To learn more about how compounding contributes to retirement savings, see Young Investors: What Are You Waiting For? and Why is retirement easier to afford if you start early?)
Below is a list of the most common areas in which people use net present value calculations to help them make decisions and solve their financial problems.
 Mortgage payments
 Student loans
 Savings
 Home, auto or other major purchases
 Credit cards
 Money management
 Retirement planning
 Investments
 Financial planning (both business and personal)
The Bottom Line on Net Present Value
The net present value calculation and its variations are quick and easy ways to measure the effects of time and interest on a given sum of money, whether it is received now or in the future. The calculation is perfect for short and longterm planning, budgeting or reference. When plotting out your financial future, keep this formula in mind.

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