Simple Interest Calculator

Before you sign up for a bank product, instantly see "how much will I actually get at maturity" and "how much do I need to repay each month" with a fully offline interest calculator. No account, no network, no permissions required.

💰 Deposit Calculator
Enter the principal, annual rate, and term, choose simple or compound interest, and instantly get pre-tax interest, tax withheld, and the after-tax payout. The tax rate defaults to 15.4% (Korea standard) but can be edited directly to match tax-free or reduced-tax products.

📈 Savings (Installment) Calculator
Enter the monthly deposit, annual rate, and term to see the maturity payout along with pre-tax and after-tax interest.

🏦 Loan Repayment Calculator
Enter the loan amount, annual rate, and term, choose a repayment method (equal principal & interest / equal principal / lump-sum), and get the monthly payment and total interest.

📊 Principal vs. Interest Visualization
See the ratio between principal and interest at a glance with a simple bar chart on the results screen.

🌏 Korean / English support
Pick your preferred language right in Settings.

🔒 Privacy-friendly
No sign-up or login needed. Amounts and rates you enter are stored only on your device and never sent to any server.

Deposits, savings, loans — let Simple Interest Calculator handle the math.

Recent changes:
Ads have been removed entirely for a cleaner experience. Added a copy button on the result card, a reset button in the top bar, and one-tap amount presets (+1M/+10M/+50M/+100M KRW) on principal-type fields for faster input. Input validation is now stricter, with specific error messages when a field exceeds its limit.