What if?

  1. The question

    What if I invested $500 a month?

    $500 monthly into the S&P 500 since 2015 — historical contributions, ending value, and SteadyGrow adaptive sizing vs blind DCA.

    Quick answer

    If you invested $1000/month into S&P 500 from 2020-01-03 through 2026-09-04, total contributions would have been about $80,539 and a blind DCA portfolio would be worth about $143,748 (+78.5%) on this historical path — before fees and taxes.

  2. Assumptions

    What this page actually assumes

    • $500 per month into the S&P 500.
    • Monthly contribution schedule from the backtest, held through the last published date.
    • No stock picks — the index path only.
    • Compare chips let you change amount or start year without leaving the story.

  3. Historical data

    2020-01-03 → 2026-09-04

    Real S&P 500 closes from 2015. Articles love “$500 a month for 10 years at 8%”; this page uses what the market actually did in the window we have.

    Series: S&P 500. Same contribution calendar. No data before 2015.

  4. Interactive simulation

    Change the habit, stay on the real curve

    Amount
    Start year

    $1000/month · S&P 500

    2020-01-03 → 2026-09-04 · $1000/month · S&P 500

    Contributed$80,539
    Held to the last date$143,748
    Return+78.5%
    SteadyGrow value$142,581
    vs blind DCA$-1,166
    S&P 5002020-01-03 → 2026-09-04 · $1000/month
     $-1,166 vs blind (-0.8%)Ended -0.8%
    Blind DCASteadyGrow
    $0$37.5k$75k$112k$150k2020-012021-052022-092023-122025-052026-09

  5. Results

    What the numbers say

    Months × $500 is cash in. Ending value is that habit marked to the index. The weekly $500 story is a cousin with a different paycheck cadence — not the same schedule.

    Want the tool framing instead of the story? Use the monthly investment calculator or the DCA vs lump sum calculator with the same dollars.

    The chart marks portfolio value over time for blind DCA, SteadyGrow sizing, and (when shown) a same-capital lump sum. Contributed cash rises in steps; ending value is mark-to-market on the last date. Blind DCA ends about $1,166 ahead of SteadyGrow on this window — adaptive sizing is not a guarantee.

  6. What changes if…

    How did we calculate this?

    • Window: real market history from our published backtest bundle, typically from 2015 through the latest Friday in the series — we do not invent older decades.
    • Contribution calendar: the engine runs on a weekly Friday grid. A “monthly” habit is converted to an equivalent weekly cash rate ((amount × 12) / 52) so the same engine can compare habits.
    • Purchase timing: each period’s contribution is applied on that week’s bar in the series (close-based weekly path), not an intraday open fill.
    • Assets: S&P 500, Bitcoin, and other series we publish — USD only. No FX conversion.
    • Shares: fractional units are assumed. No brokerage commissions, bid–ask, or slippage are modeled.
    • Dividends / income: returns follow the wealth path in the backtest bundle for that asset (not a fixed 7–10% toy rate).
    • Blind DCA vs SteadyGrow: blind buys the same cash every period; SteadyGrow keeps the same long-run budget but sizes weeks from the model’s multipliers.
    • Lump sum (when shown): the same total cash as the DCA habit, invested on day one of the window, then marked to the same path.

    Frequently asked questions

    What if I invested $500 a month?
    From 2020-01-03 to 2026-09-04, $1000/month into S&P 500 contributed about $80,539 and a blind DCA habit ended near $143,748 (+78.5%).
    Are these numbers a forecast?
    No. They replay published market history from 2015 onward. Future returns can look nothing like this window.
    What assumptions matter most?
    Start date, contribution size, weekly vs monthly cadence, and whether you held through drawdowns. Fees and taxes are not modeled.
    Can I change the amount or start year?
    Yes — use the chips on this page when available, or open a related what-if / calculator with a different habit.
    How is this different from a 7% compound calculator?
    Fixed-rate toys assume a smooth return. We mark contributions to a real index/crypto path, including crashes in the window.
    What if I had traded instead?
    See The Boring Alternative for story-shaped counterfactuals (options losses, round-trips), then run the same dollars through an index DCA calculator.

    What if the weekly amount wasn't always the same?

    These pages fix the contribution. SteadyGrow keeps the same long-term budget and sizes weeks from valuation — more when markets are cheap, less when they're stretched.

    Get weekly signals — $29/quarterLive $500/wk experiment →Boring Alternative →