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. You can use this to help you determine some important financial situations from college funds to planning for retirement.

Let's take a look at this formula using a simple scenario: 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?

Illustrating the Net Present Value

Let's go back to our original scenario. 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 which lets you value a stream of future payments into one lump sum today, as you see in many lottery payouts.
  • Present value which tells you the current worth of a future sum of money.
  • Future value which gives you the future value of cash that you have now.

Keep one thing in mind. We can assume that an investment with a positive net present value will be profitable, and an investment with a negative NPV will end up in a net loss.

Time Value of Money

So let's go into the time value of money a little more in-depth using our same scenario. 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 who are asked this question choose to take the money today. But why? What are the advantages and, more importantly, the 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, so 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.

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Understanding The Time Value Of Money

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 which lets you value a stream of future payments into one lump sum today, as you see in many lottery payouts.
  • Present value which tells you the current worth of a future sum of money.
  • Future value which gives you the future value of cash that you have now.

Keep one thing in mind. We can assume that an investment with a positive net present value will be profitable, and an investment with a negative NPV will end up in a net loss.

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

There are five factors involved in calculating the time value of money:

  1. Number of time periods involved such as months or 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 or 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 can 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 short-term Christmas expenses loan.

With four of the five components in-hand, 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)

Basic Considerations

There are a few things you may need to consider when you use these formulas. When you're applying these to your financial scenarios, there may be some error because you're basing your calculations on assumptions and estimates. They do not take into account any additional or unforeseen expenses. Furthermore, there are also other factors that may come into play including changes to interest rates that may result in volatility in your investments. So keep this in mind when you try to calculate the future value of your contributions.

The Bottom Line

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 long-term planning, budgeting or reference. When plotting out your financial future, keep this formula in mind.