Compound Interest
Compound Interest — runs in your browser. Inputs are not stored.
Compound interest
Enter values, then press Calculate.
※ FV = principal × (1 + r/n)^(n×years). Tax of 15.4% applies to interest only. May differ from actual products and tax law.
How to use
- Enter principal, annual interest rate, and term (years).
- Choose whether interest compounds annually or monthly.
- Turn on interest income tax 15.4% (Korea) if you want a general taxable assumption.
- Press Calculate for future value, pre-tax interest, tax, and after-tax amount.
- For monthly installment savings, use the installment-savings interest calculator.
Key concepts: compound interest and future value
Compound interest adds interest to principal so interest earns interest. Future value FV = principal × (1 + r/n)^(n×years). Annual compounding is n=1; monthly is n=12. At the same annual rate, monthly compounding often looks slightly larger.
The tax option multiplies 15.4% on interest only. Follow product terms for tax-exempt or separately taxed products. A lump-sum simple-interest comparison is closer to the deposit interest calculator. Results are for reference.
Example
Principal 10 million KRW, 4% a year, 5 years, annual compounding: FV = 10 million × (1.04)^5 ≈ 12.16 million KRW. Switching to monthly compounding adds a little more interest. Turning on 15.4% shows after-tax receipt after tax on the interest.
Related: deposit interest · installment-savings interest · percent calculator
Frequently asked questions
Where does tax apply in the compound-interest calculator?
If the option is on, 15.4% applies to interest only. It is not applied to principal.
Is daily compounding supported?
Annual and monthly compounding only.
What if I add money every month like a savings plan?
This screen is a one-time lump principal. For monthly deposits, use the installment-savings interest calculator.
How is it different from simple interest?
Simple interest accrues on principal only. You can compare simple vs monthly compound in the deposit interest calculator.
Why does it differ from a bank app?
Day-count conventions and interest-pay dates are not applied.
Is the principal saved?
No. Calculation runs only in the browser.
Last reviewed: 2026-09-04