STOCK
Equity simulation
Real ticker history · adjusted close · dollar-cost averaged.
We take the real, historical month-by-month price of the stock you pick and replay it — adding the money you said you'd invest along the way — so the result reflects what actually would have happened, not a guess. Dividends and splits are already baked into the prices we use, and every contribution is dollar-cost averaged in at real month-end prices.
How it works
01
We pull the stock's real past prices.
You choose a ticker (e.g. AAPL). We look up its actual monthly closing prices from Yahoo Finance, going back as many years as your chosen horizon.
02
We apply each month's real ups and downs.
Month by month, your balance moves by exactly the percentage the stock actually moved that month — no assumed average return.
03
We keep buying as you contribute.
Your starting amount, plus every monthly contribution, buys shares at that month's real price — dollar-cost averaging, so you buy more shares when prices are low and fewer when high.
What you put in
TickerWhich stock to simulate (its market symbol, e.g. AAPL, MSFT).
Initial investmentA one-time lump sum you start with.
Monthly contributionHow much you add every month afterward (can be 0).
Length (years)How many years to run the simulation.
Fees (%)Annual fund or management fee, if any — charged as a small monthly drag.
The equation
Vₘ = (Vₘ₋₁ + R) · (1 + rₘ) · (1 − f)
Vₘyour balance at month m (V₀ = initial investment)
rₘthe stock's real return in month m
Ryour monthly contribution
fmonthly slice of the annual fee = (1 + fee%)^(1/12) − 1
A worked example
Illustrative numbers — start with $10,000, add $500/month, no fee.
| Month | Real return | Buy price | Balance | Shares + | Total shares | Avg cost |
|---|---|---|---|---|---|---|
| Start | — | $100.00 | $10,000.00 | 100.00 | 100.00 | $100.00 |
| 1 | +3% | $100.00 | $10,815.00 | +5.00 | 105.00 | $100.00 |
| 2 | −2% | $103.00 | $11,088.70 | +4.85 | 109.85 | $100.13 |
- Month 1: ($10,000 + $500) × 1.03 = $10,815. The new $500 buys at the prior month-end price ($100) → 5 more shares.
- Month 2: ($10,815 + $500) × 0.98 = $11,088.70. The new $500 now buys at $103 → 4.85 shares, nudging average cost to $100.13.
What you get back
Total contributedEvery dollar you put in: initial + (monthly × months).
Final valueWhat the position is worth at the end.
Total profitFinal value minus total contributed.
Simple return %Profit as a percentage of what you put in.
Shares & average costHow many shares you hold and your blended buy price.
Growth rate (CAGR)The smoothed yearly growth of the balance curve.
Worst drop (max drawdown)The largest peak-to-bottom fall along the way.
NOTECAGR is measured against the initial lump sum only. When most of your money arrives later through monthly contributions, it reads higher than a true per-year return — lead with Total profit and Simple return for an honest headline.
Why "adjusted close"?
We use each stock's adjusted close, which already bakes in dividends and stock splits. So dividends don't appear as a separate line — they're already reflected in the price we use. Your returns here are total returns (price growth and dividends), with nothing left out.
Assumptions
- 01Returns are taken from the last trading day of each month — no daily resampling or interpolation.
- 02Dividends and splits are already reflected in adjusted close; no separate dividend modeling.
- 03Recurring contributions are invested at the prior month-end price and earn that month's return.
- 04The annual expense ratio is applied as a compounded monthly drag.
- 05After your investment horizon ends, the position is held flat to align with longer assets.
Key terms
TickerA stock's short market symbol (Apple = AAPL).
Adjusted closeThe closing price after accounting for dividends and splits.
Dollar-cost averaging (DCA)Investing a fixed amount on a schedule, regardless of price.
Total returnGains from both price changes and dividends.
CAGRCompound Annual Growth Rate — a smoothed average yearly growth.
Max drawdown (MDD)The worst peak-to-trough decline over the period.
Expense ratio / feeAn annual cost charged by a fund, here applied monthly.
What it is — and isn't
- ✓A faithful replay of real history for one stock, with your real contribution plan.
- ✗Not a prediction — past performance does not guarantee future results.
- ✗Not diversified — it simulates a single ticker; real portfolios usually hold many.
- ✗No rebalancing or trading strategy — just buy-and-hold with steady contributions.
- ✗No taxes on dividends or gains are modeled in this view.
FAQ
Where are the dividends?
They're already inside the adjusted-close price, so they quietly boost your returns rather than showing as a separate payment.
Does the same input always give the same result?
Not exactly — the window rolls back from the most recent settled month, so running it months apart can cover slightly different history.
Why doesn't the value grow after my horizon ends?
When you compare assets of different lengths, the shorter one is held flat afterward so the timelines line up.
Can I lose money?
Yes — if the stock fell over your window, the final value can be below what you contributed.
Source series
Audit log
v1.0Jun 20 2026First methodology page based on the actual simulation engine.