S&P 500 DCA Calculator
Backtest dollar cost averaging into the S&P 500 (via SPY) on real daily closes, or forecast a future contribution plan. The boring strategy, quantified.
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Why the S&P 500 is DCA's natural habitat
Dollar cost averaging into a broad index is the closest thing personal finance has to a consensus recommendation — and the S&P 500 is the reference index. One purchase buys a slice of 500 companies, which removes the single-company blowup risk that no schedule can fix. The bet is reduced to one assumption: that American large-cap earnings keep compounding over decades, as they have through wars, inflations, and crashes.
The index's relative calm (roughly 15–20% annualized volatility versus Bitcoin's 60%+) means DCA's cost-smoothing adds less raw edge here than in crypto — its job instead is behavioral: a payroll-synced monthly buy that happens through every headline is how ordinary savers actually capture the market's long-term return. Compare against a one-shot investment in the lump sum vs DCA calculator.
One honest caveat on the numbers: this backtest uses price-only closes. SPY has paid a ~1.3–2% dividend yield throughout its history, so a real reinvested-dividend result would be meaningfully higher than what the chart shows — treat our figures as conservative.
Average buy price (cost basis)
Each contribution buys shares at that day's close; cheap months buy more shares, pulling your dollar-weighted average below the simple average of prices.
- 01Buys execute at the next trading day's close (weekends and market holidays roll forward).
- 02Fractional shares are allowed — every dollar is invested, as most modern brokers now support.
- 03Contributions are constant nominal USD; no inflation adjustment.
- 04No commissions or spread. Dividends are NOT included — results are price-only and therefore understate real total returns.
- 01Price-only data understates SPY's true total return by roughly the dividend yield (~1.3–2%/yr historically).
- 02The S&P 500's past century of compounding is a strong base rate, not a guarantee — decade-long flat stretches (2000–2009) have happened.
- 03Forecast mode assumes constant growth; real sequences of returns matter, especially near retirement.
Is dollar cost averaging into the S&P 500 a good strategy?
It's the default strategy most credible research supports for income-based investors: broad diversification, no timing decisions, and payroll-friendly automation. Its historical weakness is only versus lump-sum investing when you already have the cash — markets rise more often than they fall.
SPY, VOO, or an index fund — does the choice matter for DCA?
For backtesting purposes they track the same index almost identically. In practice pick the cheapest accumulating vehicle your broker offers (expense ratios: SPY 0.09%, VOO/IVV 0.03%) — over decades the fee gap compounds.
Does this calculator include dividends?
No — it uses price-only closes, so results are conservative. SPY's reinvested dividends have historically added roughly 1.3–2% per year on top of the price return shown here.
How much would $100 a month into the S&P 500 become?
Run the exact window above. As a reference, the strip at the top of this page shows the trailing five years at $100/month, computed from real closes and refreshed with each data update.
Monthly or bi-weekly for index DCA?
Match your paycheck. The return difference between cadences is noise on multi-year horizons; consistency and zero-commission execution matter far more.
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