Theoretical Investment Growth Calculator Spreadsheet

This Google Sheet is programmed to help demonstrate the power of time and additional monthly contributions in compound interest.

All the user needs to do is input numbers for the following 6 values:

• Age to Start Investing
• Initial Investment Value
• Additional Monthly Contributions
• Anticipated Annual Growth Rate (%)
• Interest Rate Variance Range
• Times Compounded Per Year

After these six numbers have been entered, the Google Sheet is programmed to:

• calculate the total amount of money that has been invested by the end of the year every year for the next 40 years.
• calculate the total expected value of the investment every year for the next 40 years.
• calculate the theoretical values of the investment for an interest rate which varies any entered amount above and below the expected average annual growth rate every year for the next 40 years.
• create a graph plotting the total amount invested, the optimistic value, the expected value, and the pessimistic value vs. time.

There are two pages of the sheet.

The first page is programmed but the spaces for the values are blank so that users can input their own numbers. The second page is given as an example with realistic values.

This product can be used to model compound growth, and can also be used to demonstrate coding functions in Google Sheets or Microsoft Excel.