The data
Everything comes from Yahoo Finance’s daily price history, fetched live when you press Calculate. Yahoo publishes two prices per day: the close, already adjusted for stock splits, and the adjusted close, which is also adjusted for dividends using the same convention as the major index providers. Splits are already baked in, so nothing is ever multiplied by a split ratio. Every calculation also checks the adjusted close against the list of dividends paid. Where they disagree for a known reason, such as London listings applying dividends at 1/100 of their size, the adjusted close is corrected from that list.
The calculation
Your amount divided by the adjusted close on your start date gives a share count; that share count times today’s adjusted close is your current value. This is the industry-standard total return, and it is mathematically the same as reinvesting every dividend on its ex-date.
The same arithmetic on the split-only close gives the price return: capital gains with no dividends at all. With the Reinvested dividends switch off, the result is that price return plus the cash dividends you would have collected and left uninvested. With it on, the result is total return. If the stock paid no dividends over your period, the switch is greyed out, since both give the same figure.
Why the dividend figure is more than the cash paid
The results show how much dividends added to your return. That figure is larger than the cash dividends paid, because each dividend bought more shares and those shares also rose in value. $10,000 in AAPL from January 2, 2020 to December 31, 2025:
Gain without dividends$26,206 (+262.1%)
Gain with dividends reinvested$27,514 (+275.1%)
Added by dividends$1,308
Cash dividends paid$739
Growth of the shares those dividends bought$569
How results are checked
Every dividend breakdown is calculated two independent ways. The first uses Yahoo’s adjusted close, the same standard index providers use. The second rebuilds your share count from scratch, adding the shares each dividend payment would have bought, one payment at a time.
The two results must agree within $1 (or 0.01% of the return) before the breakdown is shown. If they don’t, or the price data can’t be verified, you still get the total return, but the dividend switch is greyed out and a note explains why.
What it leaves out
- Taxes, fees and commissions. Everything is gross.
- Your start is the first trading day on or after your date; “as of” is the last completed trading day. Dividends reinvest on the ex-date, the index convention, so a real brokerage DRIP would differ slightly.
- Data quality is Yahoo’s. And past performance says nothing about the future.
total = amount ÷ adjclosestart × adjclosenow
price = amount ÷ closestart × closenow
dividends = total − price
