About
Last updated: 2026-06-25
InvestGyesan is a free collection of investment calculators for average cost, ROI, dividends, the Rule of 72 and compound interest.
Every calculation runs in your browser, and we provide everything transparently based on open formulas and Korea stock tax rules.
What is InvestGyesan
InvestGyesan is a free collection of tools that help you handle the profit/loss calculations you frequently run into while investing — quickly and accurately. We present easily confused concepts like cost basis, realized ROI, dividends and compounding together with their formulas so anyone can understand them.
Operating principles (E-E-A-T)
- Experience — we mirror the line-item structure used in real broker statements (buy amount, fees, transaction tax, etc.) and break results down item by item.
- Expertise — we compute using Korea stock tax rules such as the 0.18% securities transaction tax, the 15.4% dividend tax and capital-gains-tax exemption (excluding major shareholders), plus compounding and cost-basis formulas.
- Authoritativeness — we point to standards and source links from official bodies such as the National Tax Service and the Korea Exchange.
- Trustworthiness — we never hide formulas, and clearly flag estimates and assumed values. Your inputs are not collected or stored.
Data sources
The tax rates and standards used in each calculator are based on the official sources below. Rates can change each year, and we update to the latest values when they do.
- National Tax Service — dividend tax, capital gains tax, comprehensive financial income tax
- Korea Exchange (KRX) — securities transaction tax, trading rules
- Financial Supervisory Service — investor protection and general finance
A note on accuracy
All InvestGyesan results are estimates for reference, based on your inputs and open formulas. In particular, compound interest and the Rule of 72 are simulations based on assumed returns that are not guaranteed, and realized returns can vary by broker fee rate and trade timing. Investment decisions and their outcomes are entirely your own responsibility; for exact taxes and costs, defer to your broker and official sources.
Contact
Send feedback or report errors to jin@zerolabskorea.com. For how we handle personal data, see the Privacy Policy.
Last updated: 2026-06-25