Maturity Amount Calculator

Calculates after-tax interest on Korean lump-sum deposits and monthly savings, down to the won.

Deposit amount (KRW)

KRW

Term (months)

Annual rate (%)

Tax type

Standard 15.4% Preferential 9.5% Tax-free 0%

Net payout at maturity

Total principal

After-tax interest

Interest income tax withheld:0원

What this tool does

Choose a fixed deposit or an installment savings account, enter the amount, term in months, annual rate and tax type, and you get the principal, tax, after-tax interest and the amount received at maturity. For a deposit you enter the lump sum; for savings you enter the monthly contribution. It follows Korean interest-tax rules, and it is useful for seeing how much interest you actually keep before choosing a bank product.

How it is calculated

Both products use simple interest. Deposit interest is principal × annual rate × months ÷ 12. In installment savings each monthly payment earns interest only for the months it remains, so interest = monthly payment × rate × (n + (n − 1) + … + 1) ÷ 12, i.e. payment × rate × n(n + 1) ÷ 2 ÷ 12. Tax is the pre-tax interest times 15.4% for standard taxation (14% income tax + 1.4% local tax), the preferential rate you enter (default 9.5%) or 0% for tax-free, with fractions of a won dropped; after-tax interest is pre-tax interest minus tax. For example, 10 million won deposited for 12 months at 4% earns 400,000 before tax, 61,600 in tax, 338,400 after tax, and 10,338,400 at maturity. Saving 500,000 a month for 12 months at 4% gives 6 million principal, 130,000 before tax, 20,020 in tax and 109,980 after tax.

Choose the deposit or savings tab (switching fills in 10 million or 500,000 won as an example)

Enter the lump sum for a deposit, or the monthly amount for savings

Enter the term in months and the annual rate as a percentage

Choose standard 15.4%, preferential or tax-free; choosing preferential opens a rate field, default 9.5%

Read the principal, tax, after-tax interest and maturity amount

Things to know

Advertised rates are usually pre-tax annual rates. Under standard taxation you keep 84.6% of the interest.

At the same rate, savings earn a little over half the interest of depositing the same total up front, because only the first payment earns 12 months and the last earns one.

This calculator uses simple interest only; monthly-compounding products pay slightly more, so compare with the bank's figure.

Preferential and tax-free rates apply only to eligible products within set limits; check eligibility before choosing them.

The default preferential 9.5% is the rate of Korea's former tax-preferred comprehensive savings (9% income tax + 0.5% rural development tax), closed to new accounts at the end of 2014. For other low-tax products such as cooperative deposits, enter the rate your product states. Standard 15.4% is the 14% withholding rate on interest under Article 129 of Korea's Income Tax Act plus 1.4% local tax.

Closing early applies a much lower early-termination rate, so the result will differ greatly.

Tax is rounded down to the won, so bank statements may differ by a few won.

Frequently asked questions

How much do I get from 10 million won at 4% for a year?

Pre-tax interest is 400,000; minus 15.4% tax (61,600) leaves 338,400, for a maturity amount of 10,338,400. That is exactly the default example.

Why is savings interest lower than expected?

Each monthly payment stays in the bank for a different length of time. On a 12-month plan the money earns about 6.5 months of interest on average, so it never feels like the headline rate.

Where does the 15.4% interest tax come from?

Korea's 14% interest income tax plus a local income tax of 10% of that, 1.4%. If annual financial income exceeds a threshold it moves to comprehensive taxation and the rate can change.

Can it calculate compound interest?

No, both products are calculated with simple interest. A compounding product will pay slightly more, and the gap is small over short terms.

Can I still get the 9.5% preferential rate?

9.5% belongs to Korea's former tax-preferred comprehensive savings, which stopped taking new accounts in 2015; only existing accounts remain. For another low-tax product, choose preferential and enter that product's rate.

An estimate based on Korean tax rules, not professional advice. Rates and taxes vary by product and time and may change with the law.