About & Methodology
How we calculate historical dollar-cost averaging results.
What is this tool?
dcaretro.com answers one question: "If I had invested $X every month starting in year Y, what would my portfolio look like today?" It is a retrospective simulator, not a financial advisor. Numbers are illustrative only.
Price data
All prices are fetched from Yahoo Finance and refreshed daily. We use adjusted close prices — dividends reinvested and splits applied — so returns reflect what a real long-term holder would have experienced.
S&P 500 → ^GSPC (index), from 1985
NASDAQ 100 → ^NDX (index), from 1985
Bitcoin → BTC-USD, from 2014-09-17
Gold → GLD (SPDR Gold Trust ETF), from 2004-11-19
MSCI World → URTH (iShares ETF), from 2012-01-11
Non-trading-day handling
If a scheduled buy date falls on a weekend or holiday, the purchase executes at the next available trading day's close price (T+1 policy). Bitcoin trades 24/7, so no adjustment is applied. If two scheduled dates roll to the same trading day, only one purchase is recorded to avoid double-counting.
Return metrics
- Total invested — sum of all periodic purchases actually executed.
- Portfolio value — shares accumulated × most recent price in the dataset.
- Total return — (portfolio value − total invested) / total invested.
- Annualized return (IRR) — internal rate of return on the irregular cashflow series, solved via bisection on net present value. This accounts for the timing of each individual purchase.
Limitations
- No transaction fees, taxes, or currency conversion are modeled.
- ETF tracking error vs. the underlying index is not accounted for.
- Past performance does not predict future results.
- Results are in USD. Non-US investors face additional currency risk.
Contact
Questions or data issues? Reach us at hello@dcaretro.com