Investment Calculators
Free investment calculators for average cost (cost basis), stock ROI, dividend income, the Rule of 72 and compound interest.
InvestGyesan is a free collection of investment calculators that run right in your browser with no sign-up or install, covering average cost, stock ROI, dividend income, the Rule of 72 and compound interest.
Every calculation runs locally in your browser, and your inputs are never sent to or stored on a server.
Investment calculator collection
Average Cost Calculator
Find the average purchase price (cost basis) and total shares from multiple buys.
Stock ROI Calculator
Compute profit/loss and return on investment (ROI) including trading fees and tax.
Dividend Calculator
Calculate gross and after-tax dividend income (15.4% withholding) from price, yield and shares.
Rule of 72 Calculator
Estimate how long it takes to double your money at a given annual return.
Compound Interest Calculator
Simulate the future value of monthly contributions with compounding returns.
Investing Guide
A primer on stock ROI and investment taxes, all in one place.
Investing guide
Why use InvestGyesan
- Free & no install — use it right in your browser with no sign-up or app.
- No data collected — every calculation runs in your browser and inputs are never sent to a server.
- Real taxes applied — uses Korea stock tax rules such as 0.18% securities transaction tax and 15.4% dividend tax.
- Open formulas — each calculator shows its formula, method, assumptions and limits.
Every result is an estimate for reference only; investment decisions are your own responsibility. For exact taxes and costs, check your broker and the National Tax Service and Korea Exchange.
Last updated: 2026-06-25