How we calculate

Every number on this site comes from one shared, tested calculation engine and the same historical price data. Here's exactly what it does.

Price return

We buy fractional shares at the closing price of the purchase day and value them at the latest available close:

Value = Investment × (Ending price ÷ Starting price)

Both prices are split-adjusted on the same basis, so stock splits and reverse splits never create fake gains or losses. A 2-for-1 split doubles your shares and halves the price; the value is unchanged.

Total return (dividends reinvested)

When you choose + Dividends, each cash dividend is reinvested in more shares at the close on its ex-dividend date — the standard total-return convention. You only receive a dividend if you held the shares before its ex-date. Each dividend is counted exactly once. If the data source can't supply reliable dividend history (for example, for an index), the option is disabled and we show price return only.

Annualized return (CAGR)

CAGR = (Ending value ÷ Investment)^(1 ÷ Years) − 1

Years are the actual elapsed calendar days between the purchase and valuation closes, divided by 365.2425. We don't show CAGR for periods under one year, because annualizing a few weeks of returns produces misleading numbers.

Dates

• Weekends and market holidays: we use the next trading day's close and always show the date actually used.
• Before a company listed: we say so and don't move the date for you. (In Parallel Universe, it's marked unavailable.)
• Missing or suspended sessions are skipped; we never fill in prices.
• Parallel Universe values every company on the same final date — the latest close that all of them share.
• Lookback periods (1Y, 10Y…) count back calendar months/years from the latest close. YTD is measured from the prior year's last close.

Corporate actions

Splits, reverse splits and dividends come from the data feed. Ticker changes are handled by the provider (for example, Meta's history includes its years as FB). Spin-offs, mergers and delisted companies depend on provider coverage; delisted securities may not be searchable, which means lists of "winners" can suffer from survivorship bias — we flag this where it matters.

What's not included

Taxes, trading commissions, fund fees beyond what's already reflected in an ETF's price, bid/ask spreads and inflation. Results are hypothetical and for education and entertainment. Past performance doesn't predict future results.

Data

Current source: Yahoo Finance (unofficial, personal-use). Quotes show whether they are real-time, delayed or the last close, with a timestamp. Fundamentals are shown as reported by the source and may lag company filings.