It can be difficult to calculate 401k growth with a paper and pencil. However, even those with a basic knowledge of Excel can build a simple 401k calculator. The first step in this process, of course, is to open a blank worksheet in Excel. In cell A1, enter both the name of your investment (401k, Retirement Plan, etc.) and the goal amount. Label cells A2 through E2 “Interest Rate,” “Number of Periods,” “Payment,” “Present Value,” and “Type.” This will create five columns of data for you to enter in order to track your growth and monitor your progress. In cells A3 through E3, enter the corresponding information. Enter the interest rate as a number with a decimal point. For example, an 8% interest rate should be entered as 0.08. Number of Periods is the number of months (or years, if you make an annual contribution) you will be saving. When you enter your payment, put a negative sign in front of the payment. For example, if you contribute $200 a month to your 401k account, enter that value as -$200 into Excel. Present Value is whatever is currently in your retirement fund. Again, enter that amount with a negative sign in front of the number. Leave the “Type” column blank for now. In cell A4, enter the formula PV=Current Balance; Invest Your Contribution at the beginning of the period for the number of periods. So for example, if you have $10,000 in your retirement fund, your entry will look something like this: PV=$10,000; Invest $100 at 8 percent interest at the beginning of the month for 120 months. Put the same entry into cell A7. Now you are ready to make your calculations. Select cell B5. Choose the Future Values option from the Formulas menu. Enter the formula =FV(rate, number of periods, payment, present value, type). For type, enter the value 1. Enter this same formula into cell B7, but for type, enter the value 0. Your formula in B5 will look something like this: =FV(0.05, 96, -100, -10000, 1). Your formula in B7 will look something like this: =FV(0.05, 96, -100, -10000, 0). Excel will calculate based on your current savings and contributions. Make adjustments to see how you can contribute in order to reach your 401k goals.