Data & Methodology

What these calculators do

The stock and cryptocurrency calculators answer one question: if you had invested a given amount in a given year, what would that position be worth at the latest price we hold. They are historical illustrations. They do not forecast, and they are not a view on whether any asset is worth buying.

Where the current price comes from

Apple (AAPL), NVIDIA (NVDA) and Palantir (PLTR) use the latest quote from the Alpha Vantage GLOBAL_QUOTE endpoint. The value is fetched on our server and stored against the calculator, then rendered into the page you load.

Bitcoin (BTC) and Ethereum (ETH) use the CoinGecko public price API, requested by your browser when the page loads. If that request is blocked by an extension or rate-limited, the calculator falls back to the last value it holds rather than failing outright.

How often prices update

We want to be precise about this rather than imply a freshness we do not deliver. Stock quotes refresh when our price-update routine is run; it is triggered manually, not on a fixed schedule, so a quoted stock price can be hours or days old. Cryptocurrency prices are requested fresh each time you load the page. Neither is real-time market data, and neither should be used for trading decisions.

Where the historical prices come from

Historical figures come from a reference table we maintain in the calculator itself: one approximate price per calendar year, taken around January, covering 1980 to the present for Apple and shorter ranges for the newer assets. It is a fixed table, updated by hand when we review the calculator — not a live historical feed, and not a daily price series.

This matters for how you read the result. Because we hold one price per year, a calculation dated to a given year reflects that January-ish level rather than the day you have in mind. Intra-year highs and lows are invisible to the calculation.

Stock splits

The historical table is split-adjusted. Apple's 2-for-1 splits in 1987, 2000 and 2005, the 7-for-1 in 2014 and the 4-for-1 in 2020 are already reflected in the figures, as is NVIDIA's 10-for-1 in 2024. You do not need to adjust anything yourself, and share counts shown are expressed in present-day shares.

Dividends are not included

This is the most important limitation on the page. Our results are price return only. Dividends are not counted and dividend reinvestment is not modelled.

For a dividend-paying stock held over decades, total return is materially higher than price return — reinvested dividends are a large share of long-run equity returns. If you are comparing our figure against a broker statement or a total-return chart, ours will read low, and that difference is the dividends. Bitcoin and Ethereum pay no dividend, so the distinction does not arise there.

What else is left out

• Trading commissions, spreads, custody and platform fees.
• Tax of every kind — capital gains, dividend withholding, and any local wrapper treatment.
• Currency conversion. Figures are in US dollars throughout.
• Inflation. Results are nominal, so purchasing power is not comparable across decades.
• Any assumption that you could actually have bought at the price shown, in that quantity, on that date.

Corrections

If a figure looks wrong, tell us and we will check it against the source and correct the table. We would rather fix a number than defend it. Report an issue.