Investment Calculator

Starting Amount:

Investment Length (years):

Return Rate (% per annum):

Extra Contribution:

Contribution Frequency:

Investment Calculator Instructions

To use this calculator effectively, please provide the following information:

1. Starting Amount ($): Enter the initial amount of money you are starting your investment with. This amount is sometimes referred to as the principal. It can be a large amount saved up for a home, an inheritance, or the purchase price of a quantity of gold.

2. Investment Length (Years): Enter the number of years you plan to invest. Normally, the more periods involved in an investment, the more compounding of return is accrued and the greater the rewards.

3. Return Rate (%): Here you can have several choices:

  • Utilize historical returns from representative portfolios or the S&P 500 stock index fund. For instance, if the Investment Length is set to 20 years and you opt to employ historical returns from a portfolio, the calculation would involve using the annual returns for the past 20 years to determine your overall returns and final balance. The portfolios, including the Core Asset Model Portfolios, can be found in the Asset Allocation Portfolio Templates for more detailed information.
  • Three Core Asset Portfolio: 42% US Stocks, 18% International Stocks, and 40% Bonds (since 1997)
  • Two Core Asset Portfolio: 60% US Stocks, and 40% Bonds (since 1993)
  • S&P 500 stock index: represented by Vanguard S&P 500 Index fund VFINX (since 1980)

NOTE: choosing historical returns from a portfolio or a stock index is limited to the availability of their data and thus, in general, the Investment Length should be limited to the length of these investments. Specifically, for the Investment Length N, the calculator chooses the trailing (last) N years data from a portfolio or the index to calculate/simulate the gains.

  • Custom return rate: enter the annual return rate for your investment. This is the percentage increase you expect to see in your investment each year.

4. Extra Contribution ($): Enter any additional contributions you plan to make towards the investment. These can be made without them. However, any additional contributions during the life of an investment will result in a more accrued return and a higher end value.

5. Contribution Frequency (Times per Year): Enter how often you will be making additional contributions. You can choose to contribute monthly (12 times a year), quarterly (4 times a year), semiannually (2 times a year), or annually (1 time a year).

After filling in all the parameters, click the “Calculate” button to get the investment’s end balance, total contributions, and total interest. The chart in the above will also update to show the growth of these three values over time. When you hover over the chart, you will see the specific values for each year.

Investment calculator: understand the power of compound interest

Albert Einstein once said “Compound interest is the eighth wonder of the world. He who understands it, earns it; he who doesn’t, pays it”.

Compound interest is one of the most fundamental concepts in finance and a key driver of wealth accumulation. It is interest compounded on interest. It is the process by which a sum of money grows exponentially over time due to interest being continually added to the original amount and growing.

The principle is simple: the earlier and more often interest is compounded, the greater the overall return will be. This is due to the fact that each time interest is calculated and added back to the account, the sum grows larger.

How Does Compound Interest Work?

Let’s say you invest $10,000 at a 6% annual interest rate. After the first year, you would earn $600 in interest, bringing your total balance to $10,600. The following year, you would earn interest not only on your original $10,000 investment but also on the $600 in interest that you earned the previous year. Thus, the interest for the second year would be $636, and your total balance would be $11,236.

This might not seem like a big difference in the short term, but over a long period, the results can be astonishing. You can see from the investment calculator in the above. Note in the calculator, it assumes the extra contribution starts at the beginning of the very first year. So the results are different from those in the previous paragraph.

The Rule of 72

A handy tool to understand the power of compound interest is the Rule of 72. This simple rule gives you a quick estimate of how long it will take for your investment to double at a given annual interest rate. You simply divide 72 by the interest rate to get the number of years.

For example, if your money is invested at a 6% return, it will take approximately 12 years (72 divided by 6) for your money to double. This rule underscores how a higher rate of return can significantly speed up wealth accumulation.

With rule of 72, you can quickly come up with some estimate without using the investment calculator.

The Impact of Time

The power of compound interest is best observed over long periods. The longer your money can grow, the more dramatic the compounding effect becomes. This is why it’s often said that the most powerful asset any investor has is time.

If you start saving and investing early, even smaller amounts can grow into substantial sums. This is why financial advisors always stress the importance of starting to save and invest as early as possible.

The Power of Regular Contributions

Adding regular contributions to your investment can further amplify the power of compound interest. Even modest additions to your investment can lead to significant increases in the total amount over time. This is again can be seen in the above calculator.

In conclusion, understanding and harnessing the power of compound interest is crucial for any investor. It’s a powerful concept that can significantly impact your wealth-building strategy. With patience, time, and regular investments, compound interest can be your strongest ally in achieving your long-term financial goals. This is the power of long term investments.