Lump-sum deposit
Simple interest uses principal × annual rate × months/12; compound interest is converted monthly.
Deposit & Savings Calculator — After-Tax Interest Calculation
Calculate after-tax interest and maturity amount for lump-sum deposits and monthly savings with simple or compound interest.
Deposit & Savings Calculator
* Tax rates: Normal 15.4%, Preferential 9.9%, Tax-Free 0%
Deposits and monthly savings earn interest on different cash-flow patterns
A lump-sum deposit earns interest on the full principal for the selected term, while monthly savings contributions earn interest for different lengths of time. This calculator separates simple versus compound interest and normal, preferential, or tax-free treatment to estimate after-tax maturity value.
Calculation basis
Monthly savings
Each monthly contribution has a different remaining term, so simple interest applies a month-weighted schedule.
After-tax interest
Gross interest is reduced by the selected tax rate: 15.4%, 9.9%, or 0%.
How to use
- Choose lump-sum deposit or monthly savings.
- Enter amount, annual rate, period, interest method, and tax type.
- Review principal, gross interest, tax, after-tax interest, and maturity amount.
Frequently asked questions
Why does monthly savings interest look lower than a deposit?
Only the first contribution is invested for the full term. Later contributions earn interest for shorter periods, so interest differs even at the same annual rate.
What does the 15.4% tax rate mean?
It is a common Korean example for tax on interest income including local tax. Preferential or tax-free treatment depends on the product and account holder eligibility.
Do all bank products compound monthly?
No. Actual products may use simple interest, monthly compounding, or maturity interest. Check the product terms.
This tool is a general estimate. Confirm actual rates, tax treatment, and maturity amount with the relevant financial institution or professional.