How We Calculate

Yahoo Finance (stored locally): Gives us historical prices, dividend events, and stock split info for stocks and ETFs. Prices are adjusted for splits and dividends so every result reflects what a real investor would have seen.

Coin Metrics: Provides daily price data for major cryptocurrencies (Bitcoin, Ethereum, and others) in USD. Coin Metrics is a trusted, independent crypto data provider used by researchers and money managers worldwide.

What Happens if You Pick a Non-Trading Day

When you pick a date, we automatically find the closest day the market was open. Markets are not open every day. Here is how it works:

• Weekends: If you pick a Saturday or Sunday, we use the price from the Friday before, since stock markets are closed on weekends.
• Market Holidays: If the market was closed for a holiday (like Christmas or Thanksgiving in the US), we step back to find the most recent day with real price data.
• Crypto: Crypto markets are open 24/7, so any date is valid. We still check that actual price data exists for the date you pick.
• Data Check: We always confirm that real price data exists for the date we use. We never guess or estimate prices.

What Is Dividend Reinvestment?

Our "Dividend Investor" mode shows what happens when you automatically use dividend payments to buy more shares (sometimes called a DRIP, which stands for Dividend Reinvestment Plan). Instead of taking the cash, you buy more of the same stock:

• Each dividend payment buys more shares at the market price on the day the dividend is paid
• Those extra shares earn their own dividends later on
• This creates a "snowball effect" where the number of shares you own keeps growing over time without putting in extra money
• We calculate the exact number of shares bought with each dividend, including fractional shares, just like real investment apps do

How Precise Are the Calculations?

All calculations avoid rounding errors by using high-precision math. Results are accurate to the cent. Shares are rounded to six decimal places and money amounts to two decimal places, just like a real investment account.