Frequently Asked Questions
Answers to frequently asked questions about what the results mean, data sources, tax treatment, and more.
Q1.Are these calculator results the same as actual investment returns?
No. The results of this service are estimates that do not reflect taxes, trading fees, or exchange rate changes. Actual investment results differ for the following reasons: (1) Taxes: Overseas ETF capital gains tax (22% after a 2.5 million KRW deduction) and dividend income tax (15.4%) are not reflected. (2) Fees: ETF expense ratios (TER) and trading fees are not reflected (except in the fee comparison feature, where they are included). (3) Exchange rates: For overseas assets, the FX spread at the time of buying/selling is not reflected. (4) Actual trade timing: The exact dates and prices may differ. This service is for educational and reference purposes and is not a substitute for actual investing.
Q2.Why is MDD important?
MDD (maximum drawdown) is the largest peak-to-trough decline during the investment period. No matter how high the return, if you had to endure -50% along the way, many investors panic-sell. Knowing the MDD lets you understand in advance "how far my money could shrink in the worst case with this investment." This is the starting point of asset allocation and risk management. In this service, MDD is deliberately displayed prominently — because it is a metric that must not be hidden.
Q3.How is the exchange rate reflected?
When calculating overseas assets (such as U.S. ETFs), two modes are provided. (1) USD basis: reflects only the asset's own price movement, without exchange rate changes. (2) KRW conversion: applies the exchange rate at each investment point to calculate the return on an actual Korean won basis. The difference between the two figures is the FX effect. Exchange rate data is based on the Bank of Korea reference rate or major financial data providers.
Q4.How much impact do fees have?
Over the long term, the impact is substantial. A 0.5% TER difference can account for about 10% of the final assets over a 20-year compounding calculation. Example: at a 7% annual return, with 0% fees, 10 million KRW becomes 38.7 million KRW after 20 years. With a 0.5% fee (effectively 6.5%), it becomes 35.24 million KRW. Difference: 3.46 million KRW (about 10%). With a 1.0% fee, it becomes 32.07 million KRW. Difference: 6.63 million KRW (about 17%). For ETFs tracking the same index, choosing the one with the lower expense ratio (TER) is advantageous over the long term.
Q5.Where does the data come from?
It uses adjusted close prices collected from major financial data providers. Adjusted close prices retroactively apply dividend payments and stock splits to past prices, best reflecting an investor's actual total return. Exchange rate data uses the Bank of Korea reference rate, and inflation data uses Statistics Korea (Korean CPI) and the BLS (U.S. CPI). The raw data CSVs are not disclosed externally as a matter of policy. For details, see the methodology page.
Q6.Can I download the raw data?
No. The raw price data (such as CSVs) is not exposed externally as a matter of policy. This is to comply with the data providers' terms of use and to manage data quality. All calculations are performed on the server, and only the result values (return, MDD, XIRR, etc.) are provided to users. If you need price data for research purposes, use public data sources such as Yahoo Finance, Bloomberg, or Investing.com.
Q7.How are dividends handled?
Three options are provided for handling dividends. (1) Exclude dividends: reflects only price movement and ignores dividends. (2) Include dividends (reinvested): assumes dividends are immediately reinvested, maximizing the compounding effect. (3) Include dividends (cash payout): assumes dividends are received as cash and calculated without reinvestment. The default is based on adjusted close prices, in which historical dividends are already reflected in the price. Tax effects (15.4% dividend income tax) are not reflected in any of the options.
Q8.When does XIRR show as null or "cannot be calculated"?
XIRR (internal rate of return) is found through iterative numerical calculation and fails to converge in some extreme scenarios. Main cases where convergence fails: (1) When the valuation is extremely low or near zero across the entire investment period. (2) When the investment period is very short, resulting in insufficient cash flows. (3) When gains and losses fluctuate sharply. In these cases, refer to the simple cumulative return and CAGR instead of XIRR. For details on the calculation methodology, see the methodology page.
Still have questions?
For anything you can't find in this FAQ, please reach out through the contact page. For details on how calculations are done, see the methodology page.
📋 Results are based on historical data; past returns do not guarantee future returns.
📋 This service is provided for educational purposes to help you understand investing, not as investment advice.