This tool helps you calculate trailing total returns (CAGR) for a stock-like investment. It will consider the change in the price of the stock, dividends received over the time period, and splits. It assumes you start by purchasing 1 share of the stock, and it will reinvest the dividends from that point on.
This tool makes it easy to answer questions that involve calculating returns over arbitrary time windows like:
Note: This tool is in Beta.
This tool computes returns using market prices, not NAV. This is in contrast to Morningstar, whose trailing total returns are NAV based. I prefer calculating returns based on market prices, because you & I pay market prices when we buy and sell the stocks. But, if you wonder why the returns listed in this tool don't always exactly match up with Morningstar's Trailing Total Returns, that's probably the reason.
A note on accuracy: this tool uses free data from Yahoo Finance. Free data (and even commercial data) has a history of being flawed, especially when complicated stuff happens, like buying/selling off part of the company in exchange for part of another company. This isn't a problem unique to this tool. If you look carefully - like I have - at other calculators found on the web, many of them give different results, and sometimes wildly so. I added code which analyzes the data, looking for obvious flaws, so that the tool can report them to you - making you aware that the accuracy of the data and results are suspect. But, many data anomalies are hard or impossible to auto detect, so don't rely too heavily on this feature. While I pledge to disclose any known accuracy flaws in this tool, being shrewd and doing your own due diligence is still your responsibility, not mine.
I encourage you to compare the results of this tool to others like it. Pay attention to the calculation date ranges when comparing to other tools! I think you'll find this tool tends to be more accurate, but more importantly, comparisons may reveal differences you may want to know about. While this tool (and many others on the web) uses Yahoo Finance data, some use other sources, and so comparing with other tools might be revealing if there's a significant difference in the data which leads to different calculations.
Next feature: I plan to add a log that makes it easy for you to inspect the calculations. It will be a journal-style log, which will show an entry for each event. e.g.