Below is a S&P 500 Periodic Reinvestment Calculator. It allows you to run through investment scenarios as if you had been invested in the past. It includes estimates for dividends paid, dividend taxes, capital gains taxes, management fees, and inflation. Click the button labeled 'Click to Show Advance' to show the tool's advanced options. These fields are pre-populated by the tool and we have no way to save your inputs on the server. Please make sure you back them up – paste them somewhere – if you are running a complex scenario! The tool's designed for you to set up your own defaults as two columns in your favorite spreadsheet program, then just select both columns and paste directly into the tool's text box: The tool uses data published by Robert Shiller, which you can find here. Our S&P 500 methodology from our and Dow Jones Industrial Average Reinvestment Calculator is repeated; please read those articles if you are interested in the return calculations. On top of the above features, we've added periodic investments, dividend taxes, capital gains taxes, graphing, and exporting results in monthly resolution. Here is our order of operations for every month other than the first month. In the first month, we buy shares at the market price using the lump sum, receive no dividends, and pay no fees or taxes) When we hit the closing month: Now that you've seen our methodology, a disclaimer: Everything about this tool is informational and all outputs and calculations are for research purposes only. McGraw Hill Financial owns the S&P 500 Index and decides its constituent members, you should defer to them for all exact numbers, timings, and dates. Double check all numbers output from the tool with your own calculations using source data from elsewhere.We've made every effort to present accurate information, but this calculator is maintained by a single hobbyist. There are likely errors and omissions in the data.Even when the data is accurate, choosing different timings and orderings for the steps listed above can meaningfully change the final results of the calculations.Proceed at your own risk. You can check the last updated month by seeing what was set when you opened the page. It should automatically go to the latest data. Unfortunately, we have to update manually (for now) so expect about once a month updates.We have a number of calculators pointing to the same file, so when I update one they all pick up the new data automatically; we don't have to touch each one individually: If you come back and the default dates have changed, you'll know it has recently been updated. Robert Shiller is our source, and his methodology can be found on his site.This data is reasonably accurate and I trust it, but it isn't exact and official. McGraw Hill Financial owns the S&P 500 Index; if you want more specific data on dividend timing or daily data you should seek it out from them. See Robert Shiller's site (one question above). Dates before the index are spliced to indexes which reasonably measure similar stocks. If you really don't like it, you can limit your analysis to more recent years. No, but you can. It is very easy to fill the custom advanced option fields when you use a spreadsheet program to set it up. Here's what I use (OpenOffice) - it's free. I used it to test this calculator (on a Mac), so I can vouch for it.Just paste into the fields in the advanced options. No, but you can. Try OpenOffice - it's free or Excel to lay out the dates for easy cut/paste into the tool. See the above answer, and note that when you do custom investment amounts the tool will only fill in investment amounts of the months you enter, so you can do as many or as few as you want! There are so many index funds with so many different management fees that it's impossible to have a good number. These are a reasonable start, but even today there is a huge disparity in what different funds cost to manage an index fund. Just change them if you don't like them, or start from a later date when they better match your expectations. No idea - I assume that would be the tracking error and management fee cost of large funds mimicking indexes or something. I made them up. I'm sure a large investor could pay a manager to track an index as well (or buy every stock in an index), but I agree it's not perfect - most of what we know about indexing is only a generation and a half old. All internal data is rounded off to 4 decimal places. (If you can't match a calculation exactly, that's the most likely culprit). The results are approximate anyway so this isn't a huge limitation. Still, please keep it in mind while citing and using the calculator. No. I'm available for hire if you need something custom, with this data or most any other data I have access to.The tool is in a state which makes me happy. Feel free to leave suggestions, but this is probably the final number of features that will ever be in this calculator.To project into the future, try the investment calculator instead. Here's some other work I've done... maybe I've already created what you need? Yes, absolutely... and please bring it up immediately so I can fix the tool! However, if you're trying to sneak in an enhancement request, the answer is 'no' (or 'hire me'). Consider it a reverse birthday gift - the site turned 6 years old, so you got a gift! Also, I wanted to run a lot of these scenarios myself, and you've already seen the beginnings of this calculator take shape in an article or two.Why not? The code probably took 10 or 15 hours (I don't have an exact number - it's about 1300 lines of code all in). All the miscellaneous stuff like writing this article and finding source data and defaults probably added another 5-8. With that in mind, please share this piece with all of your friends! Pure JavaScript.I used some new HTML features too for the csv export, and I use Google's library for the chart. I started it on a 2012 Macbook Pro 15", and I'm finishing up with a Mid-2014 Macbook Pro 15" Retina. So, we've addressed many of the limitations in the with this post. Now you can run wild with all of your backtesting questions on the S&P 500. I hope that this covers everything you wanted with the original tool, and additionally silences the few rumblings I still see about passive investing. Now you can run the scenario you'd like here for periodic vs. lump sum investing and see a reasonably accurate backtest. The CSV file export is another key feature. By exporting the data monthly, you can import it into your spreadsheet program and run even more complex scenarios. Also, as we showed in the original calculator, dividends matter.Over longer scenarios, you'll note that the dividends paid start to dominate the initial investment.If you ever see an article posted which ignores the effects of dividends or only quotes price returns on an index, please send the author this way!The S&P 500 Periodic Investment Calculator
Basic Options for the S&P 500 Periodic Reinvestment Calculator
Advanced Options for the S&P 500 Periodic Reinvestment Calculator
Tool Default Overrides
Methodology for the S&P 500 Periodic Reinvestment Calculator
Monthly Investment Methodology
Final Month Investment Methodology
Data Questions
How often do you update the data?
Why is the data in monthly format?Can you add daily data?
How does this dataset start from before the S&P 500 Index Began?
I don't like your management fee estimates/tax estimates. Can you change them?
My preferred investment style is (annually/quarterly/biannually/only on leap years/once per child I have), can you add it to the tool?
Are the default management fees accurate?
How do you have management fees before 1971 when the first index funds were forming?
How precise is this tool?
General Questions
Can you add <some feature I think is important> to the tool? Can you add other asset classes or indexes?
Can you fix the bug with <something I think is broken>?
Miscellaneous
Why did you make this?
How long did this take to create?
What was this calculator written in (and on)?
Conclusion for the S&P 500 Periodic Reinvestment Calculator
See Also
Investment CalculatorS&P 500 Historical Return Calculator [With Dividends] – Of Dollars And DataS&P 500 Return Calculator - Quantified StrategiesS&P 500 Return Calculator, with Dividend Reinvestment