Stock Return Calculator

How the Stock Return Calculator Works

I've designed this calculator to give you a realistic picture of long-term investment growth. It uses standard compound interest formulas with monthly compounding, which is how most brokerage accounts actually work. You don't need a finance degree to understand the results — the year-by-year table breaks everything down clearly.

The formula for compound growth with regular contributions is: FV = P(1+r)^n + PMT × [((1+r)^n - 1) / r], where P is principal, r is periodic rate, n is periods, and PMT is regular contribution. Dividends are calculated separately and can't be ignored when planning long-term.

Why CAGR Matters

CAGR (Compound Annual Growth Rate) is the single most important metric for comparing investments. It won't capture volatility, but it tells you the smoothed annual return that would produce the same final value. The S&P 500 has historically returned about 10% CAGR before inflation, or roughly 7% after inflation.

Our Testing Methodology

Every formula in this calculator has been validated against financial textbooks and cross-checked with established platforms like Vanguard's retirement calculator. Our testing includes edge cases with zero contributions, very long time horizons, and high return rates. We verify results quarterly and update the tool as needed.

Browser Compatibility

Freshness note: Tested on Chrome 134 (March 2026). All features fully functional.

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