What This Calculator Does and Doesn't Do

For the same amount and period, it compares the after-tax cash income, ending asset value, combined value, and breakeven condition of a parking account, a dividend-type asset, and a growth-type asset — all under assumptions you enter. "Asset A/B" are assumption slots you name yourself; the tool never looks up real stock data. Each asset is compared 1:1 against the parking account, assuming "if you put the full amount into each" (not simultaneous holdings or a combined portfolio).

What it doesn't do — it does not provide maximum drawdown (MDD), because the assumed price path would dominate that result. It never assigns a composite score, ranking, or "best investment" label, and it does not assign probabilities to the up/flat/down scenarios. Deposit insurance is shown only as informational (coverage/limit), never treated as "principal guaranteed," and it is not factored into the calculation.

Price and FX Path Assumption

The reinvested-dividend price and the converted exchange rate at each payment date are assumed to change evenly (in a geometric/compounding sense) across the period. The real path differs, and a different path changes the result. Geometric change is used instead of linear interpolation because, close to a −100% price change, linear interpolation would push the intermediate reinvestment price to zero or below, breaking the calculation. Since the actual payment dates aren't known, the period is divided evenly by the number of payments — this is not shown as a confirmed cash-flow calendar.

What's Included and Excluded

Included: simple interest on the parking account (after tax), the dividend withholding and reinvest/withdraw branch for each asset, adding reinvested amounts to the cost basis to prevent double-counting capital-gains tax, one-way trading and FX-conversion costs, the remaining capital-gains deduction, and the breakeven price against the parking account.
★Cost treatment differs for tax — trading commissions are recognised as transfer-expense (reflected in acquisition and disposal value), but FX conversion costs are not (NTS ruling 사전-2021-법규재산-1151). FX cost therefore reduces only your net proceeds, not the taxable gain. Expense ratio is assumed already reflected in the price change you enter, so it is not deducted again. Excluded: a real stock's actual price and dividend data, foreign tax credits and combined financial-income taxation, maximum drawdown (MDD), a combined portfolio (holding multiple assets at once), account fees beyond trading commissions, and inflation.

Reading the Result

"Principal loss" and "underperforms the parking account" are separate judgments — you can be at a loss yet still ahead of the parking account, or in profit yet still behind it. Choosing reinvestment always shows "cash received" as 0 — reinvested dividends aren't cash income; they're added to the cost basis and show up later as value when you sell. A breakeven price of "none" means that, within the range this tool can compute, no price change would make the result equal the parking account's (for example, when the dividend alone already exceeds the parking account).

Out-of-Range Inputs

A price change at or below −100% (a total loss or worse) is rejected with an error message. An exchange rate of 0 or less is also rejected. Any other server-side issue shows as a temporary error — wait a moment and try again.

Assumptions and Limits

Capital-gains tax follows the overseas-stock rule (22% after a 2,500,000-won annual basic deduction). This calculation assumes you haven't used that deduction on other overseas-stock trades this year — if you already used part of it, enter the remaining amount directly. The dividend withholding rate is an assumption that varies by country, tax treaty, and your total financial income — it is not a single fixed rate. The parking-account rate is an expected value "if the entered terms hold," not a guarantee (variable rates and promotional terms that expire both apply). Results are a reference calculation, and the investment decision and its outcome are your own responsibility.