Compare repayment methods, calculate interest & DSR, and build your own amortization plan
Understanding your mortgage loan repayment in detail can save you millions of won in interest and help you pass regulatory checks like DSR. With over 70% of Korean borrowers using equal repayment methods as of 2026, it's critical to know which option works best for you. In this guide, I’ll walk you through how to compare repayment types, build an Excel simulator, use online tools, and make decisions with real-life data. Whether you're a first-time homebuyer or refinancing, this is your practical manual.
1. Comparing Mortgage Repayment Types in Korea
There are three main repayment types in Korean mortgage loans. Each has different implications for monthly cash flow and total interest burden.
| Type | Key Feature | Monthly Pattern | Total Interest | Example (100M KRW, 4%, 30yrs) |
|---|---|---|---|---|
| Equal Principal + Interest | Fixed monthly amount | Flat (higher interest first) | 72M KRW | 477,000 KRW/month |
| Equal Principal | Fixed principal, declining interest | High early → lower later | 60M KRW | Starts at 610,000 KRW/month |
| Bullet (lump sum) | Pay interest monthly, principal at end | Flat interest only | 90M+ KRW | 333,000 KRW/month (interest only) |
While equal principal saves the most interest, it comes with higher monthly payments early on. That’s why over 70% of Koreans prefer the stable equal principal + interest option.
2. How to Build a Mortgage Repayment Simulator in Excel
You can create a full simulator in Excel with customizable terms, including DSR and LTV. Here’s how to get started.
| Input | Example |
|---|---|
| Loan Amount | 300,000,000 KRW |
| Annual Interest | 4.0% |
| Term | 30 years |
| Grace Period | 0–1 year (optional) |
Use PMT for fixed payments:
- Payment: =PMT(0.04/12, 360, -300000000)
- Interest: =E7*(0.04/12)
- Principal: =B8-C8
- Balance: =E7-D8
Copy formulas for all 360 months to view total interest (~216M KRW).
To simulate equal principal:
- Monthly Principal: =300000000/360
- Interest: =E7*(0.04/12)
- Payment: =B8+C8
3. Best Online Mortgage Simulators in Korea
For quicker access, try these mobile-friendly tools. They calculate monthly payments, DSR, and let you export schedules.
| Website | Features | Inputs | Outputs | Mobile |
|---|---|---|---|---|
| best79.com | All repayment types, Excel alternative | Amount, rate, term, grace | Monthly pay, total interest, export | Yes |
| calculator.ai.kr | DSR, LTV, regulation checks | Same + LTV, DTI | DSR, LTV, monthly plan | Yes |
| ezloan.io | Graphical charts, clean UI | Basic 3 inputs | Payment breakdown + graphs | Yes |
4. DSR & LTV Explained (2026 Rules)
As of 2026, regulations cap DSR (Debt Service Ratio) at 40% for high-value homes. LTV (Loan-to-Value) depends on buyer status.
- DSR = (Annual repayments) / Annual income × 100
- Example: 24M KRW annual payments / 70M income = 34.3% (Approved)
LTV for first-home buyers: up to 80%. Home price: 500M KRW → LTV 70% → Max loan: 350M KRW
5. Real Example: 300M KRW Mortgage (30yrs, 4%)
| Month | Payment | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | 1,433,000 | 1,000,000 | 433,000 | 299,567,000 |
| 12 | 1,433,000 | 995,000 | 438,000 | 284,000,000 |
| 180 | 1,433,000 | 700,000 | 733,000 | 150,000,000 |
| 360 | 1,433,000 | 20,000 | 1,413,000 | 0 |
Total payment: 516M KRW Total interest: 216M KRW DSR (income 100M): 17% — Pass
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6. Advanced Excel Templates and Features
You can download shared Excel templates that include grace periods, variable rates, and year-end interest summaries.
- Grace period: First year interest only, then amortize
- Variable interest: Yearly rate input auto-updates schedule
- Tax deduction: Annual interest summed for refund (max 3M KRW)
Sites like Yesform or shared Naver blogs offer downloadable versions ready to plug-and-play.
7. Final Tips and 2026 Outlook
- DSR over 40%? Rejected. Stress DSR applies (add +2% to rate)
- LTV limits vary: 70~80% for first-time buyers
- Use Excel validations for dropdowns and conditional formatting for zero balances
- Interest rates in 2026 average 3.5~4.5%
— so budgeting early is wise
Try multiple scenarios with online tools and don’t forget to compare monthly cash flow vs total interest.
How to Create an Excel : Complete Guide to Equal Principal and Interest Payments and Equal Principal Payments
#mortgageloansimulator #excelamortization #koreamortgageloan #dsrcalculator #ltvratio #koreanhomeloan mortgage planning
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