Loan Interest Calculator

Calculate interest and monthly payments for mortgages, personal loans, and more. Compare equal principal & interest vs. equal principal repayment methods to find the best loan terms.

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How to Use

1. Enter Loan Amount

Enter the loan amount in KRW. For mortgages, up to 70% (LTV) of the property value is available. Personal loan limits depend on income and credit rating.

2. Enter Annual Interest Rate

Enter the annual interest rate as a percentage. Mortgage rates are typically 3.5~5.5%, and personal loan rates are 5~15%.

3. Select Loan Period

Select the repayment period in months. Mortgages typically range from 10~30 years (120~360 months), personal loans from 1~5 years (12~60 months).

4. Select Repayment Method

Equal Principal & Interest pays the same amount each month. Equal Principal divides the principal evenly, resulting in decreasing payments over time.

Real-World Examples

Example 1: First-time Home Purchase

A couple purchasing a 500M KRW apartment with 200M down payment, borrowing 300M at 4.5% for 30 years. Monthly payment: ~1.52M KRW, total interest: ~250M KRW.

Example 2: Business Operating Fund

A cafe owner borrowing 50M KRW at 7% for 3 years for renovation. Monthly payment: ~1.54M KRW, total interest: ~5.5M KRW.

Example 3: Jeonse Deposit Loan

Borrowing 300M KRW at 3.2% for 2 years for apartment deposit. Interest-only payments for first year (~800K/month), then principal repayment begins.

Tips to Reduce Loan Interest

  • Compare rates across multiple banks - even 0.5% lower saves millions
  • Check and improve your credit score before applying
  • Start repaying immediately without grace period to reduce total interest
  • Choose products without early repayment penalties
  • Exercise your annual rate reduction request right
  • Check if income deductions are available for your loan type
  • Set loan limits generously but only use what you need

FAQ

Which repayment method is better?

If your income is stable, Equal Principal saves 10~20% on total interest. For a 300M KRW loan at 4% over 20 years, the difference is about 7M KRW. However, if cash flow is tight initially, Equal Principal & Interest offers more predictable payments.

How are loan interest rates determined?

Rates = Base rate + Spread. Base rates follow the Bank of Korea rate or COFIX. Spread depends on credit rating (0~5% difference), income, collateral value, and loan term.

What are early repayment penalties?

Early repayment fees are typically 0.5~1.4% of the repaid amount, charged within the first 3 years. Low-income borrowers may be exempt since 2023.

What are LTV, DTI, and DSR?

LTV (Loan-to-Value): max loan vs. property value (typically 70%). DTI (Debt-to-Income): annual repayments vs. income (max 50%). DSR (Debt Service Ratio): stricter than DTI, includes all loans (max 40%).

How long does loan approval take?

Personal loans: 1~3 days. Mortgages: 1~2 weeks. Prepare income verification, ID, and other documents in advance for faster processing.

When should I refinance?

Refinance when rates drop 1%+ below your current rate. Consider early repayment fees (0.5~1.4%) and new loan fees (~500K KRW). A 1% reduction on 200M KRW over 10 years saves ~10M KRW.

What is the difference between interest-only and standard loans?

Interest-only loans defer principal payments for 1~3 years, reducing initial burden but increasing total interest by 20~30%. Plan carefully as payments increase significantly after the grace period.

Disclaimer

This calculator is for reference only. Actual loan terms vary by bank, credit rating, income, and collateral. Please consult a financial institution for accurate rates and conditions. Excessive borrowing may affect your credit score.

The Principles and Structure of Loan Interest Calculation

Loan interest is the cost a financial institution charges for lending money, calculated by applying an interest rate to the principal. Interest rates are expressed as annual rates (APR), and monthly calculations use the annual rate divided by 12.

Equal Principal & Interest vs. Equal Principal: Key Comparison

Equal Principal & Interest (annuity) payments stay the same every month, with interest making up a larger share early on and the principal share growing over time. Equal Principal payments divide the principal evenly each month, with interest added on top, meaning payments start high and decrease. Equal Principal suits borrowers with stable income and upfront cash, while Equal Principal & Interest suits those who prefer predictable monthly expenses.

Practical Tips for Comparing and Reducing Loan Costs

The most effective way to reduce loan interest is to compare rates across multiple financial institutions. Mortgage rates can differ by 0.3–1% between banks, and a 0.5% rate difference on a 300M KRW loan results in about 25M KRW more in interest over 30 years. Managing your credit score to reduce the spread, choosing products with no early repayment fees, and selecting between fixed and variable rates based on market conditions are all key cost-reduction strategies.

This calculator is provided for informational purposes only.

Results are estimates and may differ from actual amounts.

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