What is a Loan Repayment Calculator?
A loan repayment calculator automatically computes how much you need to pay each month and the total interest on your loan. It can be used for various loan products including mortgages, personal loans, and auto loans.
This calculator supports three major repayment methods: Equal Payment (amortized), Equal Principal, and Bullet (interest-only). You can compare monthly payments and total interest for each method at a glance.
Key Features
3 Repayment Methods
Supports equal payment, equal principal, and bullet repayment methods to help you find the best option for your situation.
Monthly Repayment Schedule
View detailed breakdown of principal, interest, payment amount, and remaining balance for each month.
Method Comparison
Compare monthly payments and total interest side by side across all three repayment methods to choose the optimal one.
Auto Number Formatting
Amounts are automatically formatted with thousand separators for easy reading of large numbers.
How to Use
- Enter Loan Amount -- Enter the total loan principal amount.
- Enter Interest Rate -- Enter the annual interest rate (%) for the loan product.
- Set Loan Period -- Enter the loan period in years or months.
- Select Method and View Results -- Click on the Equal Payment, Equal Principal, or Bullet tab to see monthly payment, total payment, and total interest. Click Show Repayment Schedule for monthly details.
Use Cases
Mortgage Comparison
Compare monthly payments and total interest across different bank rates when purchasing a home to find the best loan terms.
Auto Loan Planning
Calculate monthly payments based on different loan periods and interest rates when buying a car to plan your budget.
Rental Deposit Loan Review
Compare monthly burden across different repayment methods for rental deposit loans to set an appropriate loan limit.
Refinancing Analysis
Calculate and compare interest on your current loan vs. a new loan to see how much you can save by refinancing.
Frequently Asked Questions
What is the difference between Equal Payment and Equal Principal?
Equal Payment (amortized) pays the same total amount (principal + interest) every month. Initial burden is lower but total interest is higher. Equal Principal pays the same principal amount each month plus interest on the remaining balance. Initial payments are higher but decrease over time, resulting in less total interest.
When is Bullet repayment advantageous?
Bullet repayment pays only interest during the loan period and repays the full principal at maturity. Monthly burden is the lowest but total interest is the highest. It is suitable when you need short-term funds or expect a lump sum at maturity.
Which repayment method is best for a mortgage?
Equal Payment is the most common for long-term mortgages. It makes household budget management easy since you pay the same amount each month. If you can afford higher initial payments, Equal Principal can reduce your total interest.
Are early repayment fees included in the calculation?
This calculator provides basic principal and interest repayment calculations. Early repayment fees, origination fees, and other charges are not included. Please check with your bank for actual loan details.
Can the calculation results differ from actual bank loans?
This calculator uses standard formulas. Actual bank products may differ due to interest calculation dates, fees, preferential rate applications, etc. Please contact the specific financial institution for exact figures.
Privacy Notice
This loan repayment calculator processes all calculations in your browser. No entered amounts or interest rates are sent to any server. You can use it with confidence.
Understanding Loan Repayment in Depth
Even with the same interest rate and the same principal, the repayment method and rate type you choose can change your monthly payment and lifetime total interest by millions of won. Layer on Korea's tightened DSR and LTV rules as of 2026, and simply hunting for 'the lowest rate' is no longer enough. This article breaks loans down from three angles: repayment-method comparison, fixed-vs-variable rate selection, and the 2026 borrowing-limit regulations.
Equal Installment vs Equal Principal vs Bullet — What Differs
There are three main repayment methods. Equal principal-and-interest (equal installment) keeps your total monthly payment (principal + interest) constant; early on, interest makes up most of it and principal shrinks slowly. Equal principal keeps the principal portion constant each month, so interest on the remaining balance falls over time — the early burden is highest but monthly payments drop later and total interest is lower. Bullet repayment means paying only interest throughout the term and repaying the full principal at maturity: lowest monthly burden, but highest total interest.
- Equal installment: easy household cash-flow forecasting; the most common form for mortgages
- Equal principal: minimizes total interest; favorable for those with early repayment capacity
- Bullet: suits jeonse deposit loans or short bridge loans where a lump sum is coming soon
Worked Example — KRW 100M, 5% APR, 30 Years
Suppose you borrow KRW 100 million at 5% (0.41667% monthly) over 360 months. With equal installment, the monthly payment using P×r×(1+r)^n ÷ ((1+r)^n−1) is about KRW 536,800, and total repayment over 30 years is roughly KRW 193.26M — so total interest is about KRW 93.26M. With equal principal, month one is KRW 277,778 principal + KRW 416,667 interest = about KRW 694,400, falling roughly KRW 1,160 each month down to about KRW 279,000 in the final month. Equal-principal total interest is about KRW 75.2M, saving roughly KRW 18M versus equal installment — at the cost of about KRW 160,000 more in early monthly burden.
| Method | Early monthly payment | Late monthly payment | Total interest (30yr) |
|---|
| Equal installment | ~KRW 537K | ~KRW 537K | ~KRW 93.26M |
| Equal principal | ~KRW 694K | ~KRW 280K | ~KRW 75.2M |
| Bullet | ~KRW 417K (interest only) | KRW 100M lump sum | ~KRW 150M |
Fixed vs Variable (COFIX) Rates
A variable rate is usually set as COFIX plus a spread and resets every 6 or 12 months to reflect market rates. It helps in a falling-rate environment but raises your burden when rates climb. A fixed rate stays locked for the contract term, offering predictability, though the starting rate tends to be somewhat higher than variable. Generally, if your term is long and you can't absorb rate swings, consider fixed (or hybrid); for short holding periods or a near-term refinance, variable may fit.
2026 DSR, LTV, and Stress-DSR Rules
How much you can borrow is governed by DSR (Debt Service Ratio). Annual principal-and-interest across all your loans cannot exceed 40% of annual income at banks, or 50% at non-bank lenders. The nationwide Stress DSR Stage 3, in force since July 2025, adds a 'stress rate' on top of the actual rate to compute limits more conservatively — +3.0%p for mortgages in the capital region/regulated zones, +0.75%p for provincial areas (temporary). LTV in regulated zones was also tightened from 70% to 40%, cutting the absolute amount you can borrow against value. Choosing a variable rate applies a larger stress add-on, shrinking your limit by roughly 10–15%.
- DSR tip: credit loans, card loans, and jeonse loans all count, so paying down existing debt before applying raises your mortgage limit
- Grace period: interest-only periods lower the early burden but increase total interest and can hurt DSR calculation
- Early repayment fee: the January 2025 reform cut the five major banks' mortgage fees to around 0.65%, making refinancing or early payoff lighter than before (typically waived after 3 years)
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