About this page
A free calculator. Everything is worked out in your browser; nothing you type is sent anywhere.
How to read it
- Rate
- The yearly percentage your money grows or costs.
- Compounding
- Earning returns on earlier returns, which makes growth speed up over time.
A real example
$1,000 that grows 7% a year becomes about $7,612 after 30 years, because each year's growth is added before the next year's is counted.
Explain it like I'm 13
If you plant one apple seed and each tree gives you seeds to plant next year, the orchard grows faster every year. A calculator shows how fast.
Data from public SEC filings and congressional reports. Information, not investment advice. Check every number against the filing linked on the page.
Insider Buying Backtester
What would have happened if you had bought every stock that insiders bought, under your own rules? Pick the rules; we check every matching purchase in our records against the S&P 500.
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How it works
For every insider purchase in our records that matches your rules and is old enough to measure, we take the stock's change from the week of the purchase to the end of the holding period, and the S&P 500's change (SPY) over the same weeks. Each purchase counts once, equally, as if you had put the same amount into each. Prices are weekly closing prices from SEC fails-to-deliver data, so this is an approximation: it leaves out dividends, trading costs, taxes, and the days between the trade and the filing, when the price may already have moved. Windows that cross a likely stock split are skipped.
A rule that worked in the past can stop working, and a small number of purchases can make any rule look good or bad by luck. This is a learning tool, not advice.
Examples
Researchers have studied this for decades. A well-known 1998 study by H. Nejat Seyhun, Investment Intelligence from Insider Trading, found that stocks bought by insiders tended to do better than the market afterward, while sales said much less. Our backtester lets you test the same idea on recent filings.
Explain it like I'm 13
Imagine a game where, every time a team's coach bets on their own team, you make the same bet. This tool looks back at all those times and adds up whether copying the coaches would have beaten just betting on every team at once.