Compounder

See what the money you're about to spend could grow into if invested in the S&P 500. 100% local — nothing leaves your browser.

Compounder turns the price in front of you into a simple what-if: how much could this money grow if you invested it in the S&P 500 instead of spending it? At checkout, a small card projects your cart total forward using the S&P 500's long-run historical average return. On any product page, click the toolbar icon to see the same projection for the item you're viewing. Choose a 10, 20, or 30-year horizon and see both the nominal figure and an inflation-adjusted "in today's money" value. Everything is calculated locally in your browser. Compounder makes zero network requests — no analytics, no tracking, no accounts. It's a private thought experiment, not financial advice; past performance doesn't guarantee future results.