If your company offers a 401(k) savings option, you are fortunate, especially if your company offers matching contributions. This can help you boost your retirement savings quickly. Knowing how to build a 401(k) projection calculator in Excel allows you to see how changes to your plan will affect your retirement income.
Calculating Annual 401(k) Contribution
Before you can build a 401(k) Excel formula, you need to understand how 401(k) savings are calculated. The formula is similar to finding out how much you will have saved over any interval of time with regular contributions. To build a 401(k) growth calculator in Excel, you need to know the rate at which your savings will grow. You can usually get this information from your human resources department or plan manager.
If you have several different instruments, such as a mutual fund, bonds and another savings plan, you can run the calculator for all of them and then add the results together. You will need several pieces of information for the 401(k) projection calculator in Excel. Here is what you will need.
PMT: This number assumes regular contributions. You will need to add your employer contributions and your contributions, either together or separately. Considering them separately allows you to see what would happen if you changed your contribution.
NPER: This refers to the number of payment periods. You can calculate the number of payments per year based on whether you receive your pay weekly, bi-weekly or monthly. This can be multiplied by the number of years until retirement to calculate the NPER.
PV: This is the value of the total amounts of the contribution that the investment is worth now.
FV: This value tells you what the future value of an investment is worth based on constant payments and a constant interest rate.
401(k) Growth Calculator in Excel
A 401(k) projection calculator in Excel assumes a constant interest rate for simplicity. You must also be aware that creating the calculator might be slightly different depending on the version of Excel that you have. Here is the formula for creating the 401(k) growth calculator in Excel.
The first thing you need to do is to create columns for all the variables. It is suggested that you put them in the order listed in the 401(k) Excel formula, with the exception of FV, which should be the last column. Next, you need to plug the numbers into the columns, For the rate, you can either use the number provided to you by the plan manager, or you can usually assume 7 percent, which is the average growth of the stock market over time. The number that you will use is:
In this case, it would be 7 percent/ 12 = 0.5833.
If you are going to retire in 20 years, the NPER would be:
20 years * 12 months in a year = 240
One thing to note is that the PMT is your contribution, which can either be your contribution and your employer’s contribution combined, or you can run them separately in two different columns and add them together in a third column. This allows you to manipulate how changes in your contribution affect the 401(k) Excel formula results. Both the PMT and PV are entered as negative numbers because it is considered payment from you. The PV is the amount you have in the account now.
Things to Consider
The calculator assumes constant contributions and a constant growth rate. Other things that might affect the 401(k) Excel formula are taxes and contribution limits. This is a simplified version and will give you a general idea of what you will have if you start now. Many 401(k) companies and managers offer a similar projection tool on their websites.
Adam Luehrs is a writer during the day and a voracious reader at night. He focuses mostly on finance writing and has a passion for real estate, credit card deals, and investing.