Loan Interest Calculator — How to Calculate Monthly Repayments (Equal Principal+Interest vs. Equal Principal)
Jun 21, 2026
Before taking out a loan, the two questions everyone wants answered are: "How much do I repay each month, and how much will I pay in total interest?" Even with the same loan amount and interest rate, the monthly payment and total interest will differ depending on your repayment method. This guide explains how to calculate monthly loan repayments and total interest.
Enter your loan amount, interest rate, and term to see your monthly repayment and total interest for each repayment method.
Loan Interest Calculator →Repayment Methods — What's the Difference?
- Equal principal + interest (원리금균등) — You pay the same fixed amount every month. Easy to budget for, and the most commonly used method in Korea.
- Equal principal (원금균등) — You repay the same portion of principal each month, while the interest portion decreases over time. Payments are higher at the start, but total interest paid is lower.
- Bullet repayment (만기일시) — You pay only interest each month and repay the entire principal in one lump sum at the end of the term.
How to Calculate — 1 Step
- Enter your loan amount, annual interest rate, and term (in months) into the Loan Interest Calculator. Your monthly payment, total interest, and total repayment amount are shown instantly for each repayment method.
When to Use This
- Estimating your monthly payment burden before taking out a home mortgage or personal loan.
- Comparing interest rates and term lengths across multiple banks.
- Checking how much interest you'd save by making an early repayment or refinancing.
Related Calculators
To check how much of your salary you can comfortably put toward repayments, try the After-Tax Salary Calculator. For building up a lump sum, use the Savings & Deposit Calculator. For jeonse (전세, a Korean lump-sum deposit lease) or monthly rent conversion, try the Jeonse/Monthly Rent Conversion Calculator.
Calculates for both equal installment and equal principal methods. Free.
Loan Interest Calculator →Frequently Asked Questions
Q. Which repayment method is better?
In terms of total interest, equal principal repayment costs less overall — but your initial monthly payments are higher. If you prefer a predictable fixed payment each month, equal principal + interest is the more straightforward choice.
Q. Does the calculator account for early repayment fees?
The base calculation covers principal and interest only. Early repayment fees vary by lender agreement, so you'll need to check those separately with your bank.
Q. Is the data I enter sent anywhere?
No. All calculations are performed locally in your browser — nothing is stored or transmitted.