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Comparison by Simple Interest, Compound Interest, After-tax Interest, and PeriodInterest calculator

Enter the principal, annual interest rate, and period to instantly calculate simple and compound interest, the amount received at maturity, and the after-tax amount.

💵 Simple Interest📈 Compound Interest Comparison💰 After-tax calculation📋 Table by Period
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💵 Enter Interest Information
principal10 million won
원
10,000250 million500 million750 million1 billion
Annual interest rate5.0%
%
0.1%7%15%22%30%
period3 years
년
1 year7 years15 years22 years30 years
Calculation method
💡 Simple interest: Interest only on the principal · welfare: Interest on interest. Interest income tax 15.4% The after-tax amount is also displayed.
📊 Calculation result
💵

After entering the principal, interest rate, and period
Calculate Please press the button.

Total interest (simple interest)
—
—
Total amount at maturity—
After-tax interest (15.4%)—
After-tax maturity amount—
principal—
Rate of return—
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What is an interest calculator?

An interest calculator is a tool used to check interest generated from deposits, bonds, and short-term fund management in advance. It can be used to compare simple and compound interest to determine which product is more advantageous.

Simple Interest Calculation Formula

Total Interest = Principal × Annual Interest Rate × Period (Years)
Maturity Amount = Principal + Total Interest

Compound interest calculation formula

Maturity Amount = Principal × (1 + Annual Interest Rate)^Period (Years)
Total Interest = Amount at Maturity − Principal

What is interest income tax?

Interest income tax on interest and dividend income generated from domestic financial products 15.4%(Income tax 141 TP3T + Local income tax 1.41 TP3T) is withheld. You can save on taxes by using an ISA account (tax-exempt up to 2 million won per year) or tax-exempt savings products.

How to use this calculator

  • When quickly comparing the simple interest income of various deposit products
  • When checking the difference between simple and compound interest directly in numbers
  • When selecting a product by calculating real after-tax profit
  • When checking basic figures before moving on to the compound interest calculator

Frequently Asked Questions

What is the difference between simple interest and compound interest?
Simple interest is a method where interest is applied only to the principal. Compound interest is a method where interest is applied again to the accrued interest, and the difference widens significantly as the period lengthens. For example, if you invest 10 million won for 10 years at an annual rate of 5%, the interest generated is 5 million won under simple interest and approximately 6.29 million won under compound interest.
How much is the interest income tax?
Withholding tax of 15.41 TP3T (income tax 141 TP3T + local income tax 1.41 TP3T) is levied on domestic financial interest income. By using an ISA account, you can receive tax exemption benefits up to 2 million won annually, with a separate taxation rate of 9.91 TP3T on the excess amount.
I want to calculate compound interest in more detail.
You can find more detailed calculations for monthly installment compound interest and periodic compound interest (monthly and quarterly) on the compound interest calculator page.
Is the after-tax amount calculated accurately?
The after-tax calculation in this calculator is based on an interest income tax of 15.41 TP3T. For those subject to comprehensive taxation on financial income (when annual income exceeds 20 million KRW), additional taxes may apply, so the actual after-tax amount may differ.

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