You could have shared an image of the tool however I took the risk and here's what it says if you invest $250 every month for the past 5 years vs S&P500. (311.94%   Profit)


I have few suggestions, reduce the number of clicks I need to make. Just show me the chart/values with the default values.
Also, you can have the options on the left and the numbers on the right. (Left for Form Inputs, Right for Results).