Loan Repayment Calculator

Compare Equal Installment, Equal Principal, and Bullet loan payments and view a full repayment schedule.

Calculated instantly as you type · Amounts and rates are not sent to the server

Loan Conditions

Loan Amount (KRW)

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Annual Interest Rate (%)

Monthly rate = Annual rate ÷ 12

Term

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Grace Period (Months, optional)

During the grace period, only interest is paid, not principal.

Extra Monthly Payment (KRW, optional)

Prepayment simulation

Calculation Results

—Monthly Payment (KRW)

—Total Interest (KRW)

—Total Repayment (KRW)

—Payments

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Repayment Method Comparison (Same Conditions)

Method	First Payment	Last Payment	Total Interest	Total Repayment	vs. Equal Installment

Repayment Schedule

Payment #	Payment Amount	Principal	Interest	Remaining Balance

⚠️ This calculator assumes a fixed interest rate, monthly compounding, and no fees, and is for reference only. Actual loan amounts may vary depending on product terms such as variable interest rates, daily interest calculation, differences in the number of days for the first payment, stamp duty and mortgage setup fees, and prepayment penalties (typically 0.5-1.5% of the remaining balance within 3 years). Please confirm the exact repayment amount with the repayment schedule provided by your bank.

📐 Equal installment monthly payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1) (P=principal, r=annual rate÷12÷100, n=total months). For equal principal repayment, each month, P÷n in principal is paid, plus interest on the remaining balance for that month; for bullet repayment, only P×r in interest is paid each month, with the full principal repaid in the final installment.

What is the Loan Repayment Calculator?

The same loan amount and interest rate can result in vastly different total interest paid depending on the repayment method. This calculator instantly compares three common methods—Equal Installment, Equal Principal, and Bullet Payment—showing you the difference in total cost. It also generates a complete, payment-by-payment schedule so you can see how your balance decreases over time. Simulate adding a grace period or making extra monthly payments to see how much interest you can save. All calculations run in your browser; your financial data is never sent to a server.

How to use

Enter the `Loan Amount (KRW)`, `Annual Interest Rate (%)`, and `Term` in years or months.
Select a primary repayment method to analyze: `Equal Installment`, `Equal Principal`, or `Bullet Payment`.
Optionally, enter a `Grace Period (Months, optional)` or an `Extra Monthly Payment (KRW, optional)` to model different scenarios.
Review the `Calculation Results` and the `Repayment Method Comparison` table, which calculates all three methods simultaneously.
Scroll through the `Repayment Schedule` to see the breakdown of principal and interest for each payment.
Click `Save Schedule CSV` to download the full table for use in a spreadsheet.

Loan Repayment Calculator guide

How this tool is used in real work, and what to watch out for.

Equal Installment vs. Equal Principal — How to Choose

If you only look at the total interest, the answer is simple: Equal Principal is always cheaper. That's because you pay off the principal faster from the start, reducing the balance more quickly, and interest is calculated on the remaining balance. Still, most people choose Equal Installment because of the lower initial payments.

For a 100 million won loan at 3.5% for 30 years: with Equal Installment, you pay a fixed 449,045 won each month, for a total interest of about 61.66 million won. With Equal Principal, your first payment is 569,444 won, decreasing to 278,588 won by the last payment, with a total interest of about 52.65 million won. The total interest is 9 million won less, but the first month's payment is 120,000 won higher. The real deciding factor is whether you can afford that extra 120,000 won each month.

	Equal Installment	Equal Principal	Bullet Payment
Monthly Payment	Fixed until the end	Highest at first → decreases monthly	Interest only → full principal at maturity
Total Interest (100M won·3.5%·30yr)	Approx. 61.66M won	Approx. 52.65M won	105M won
Initial Burden	Low	High	Lowest
Budgeting	Easy — same amount each month	Changes every month	Easy (until maturity)
Best For	Salaried workers with a steady income	When you can afford higher initial payments and want to save on interest	When a lump sum is guaranteed at maturity (e.g., from a sale, deposit return)

Note that the total interest for the Bullet Payment is 105 million won. Because the principal remains unchanged for 30 years, the interest paid exceeds the principal. This is not a repayment method you should choose without a solid plan to repay the principal at maturity.

The Grace Period Trap — It Doesn't Reduce Your Interest

A grace period is a time when you only pay interest, not principal. It seems attractive because the immediate payments are low, but you need to understand what's really happening.

On the same 100 million won, 3.5%, 30-year loan, let's add a 36-month grace period. For the first 3 years, you only pay 291,667 won (interest only) each month. But after those 3 years, you have to repay the entire 100 million won principal over the remaining 27 years, so your monthly payment jumps to 477,527 won. Without the grace period, it would have been 449,045 won. The total interest increases from 61.66 million won to 65.22 million won, an increase of about 3.56 million won.

Your balance doesn't decrease by a single won during the grace period. Since interest is charged on the balance, you pay the maximum interest amount that entire time.
When the grace period ends, your monthly payment increases because you have less time to repay the principal. Don't be overly optimistic about your income at the end of the grace period.
A grace period postpones your burden, it doesn't reduce it. In total, it actually increases it.
There are situations where a grace period makes sense — for construction loans where you only pay interest until you move in, or during clearly defined periods with no income, like the initial phase of a startup.

Enter a number in the Grace Period field and look at the repayment schedule. You'll see that the "Principal" column is 0 and the "Remaining Balance" column stays the same during the grace period.

The Power of a 1 Percentage Point Interest Rate

It might seem excessive to shop around banks just to shave 0.5 percentage points off your interest rate. The numbers tell a different story.

Comparing a 3.5% vs. a 4.5% annual rate on a 100 million won, 30-year Equal Installment loan: the monthly payment is 449,045 won vs. 506,685 won, a difference of 57,640 won per month. The total interest is 61.66 million won vs. 82.41 million won — a 20.75 million won difference. If the loan amount were 300 million won, this difference would also triple.

The longer the term, the wider the gap. On a 30-year mortgage, a 1 percentage point difference is worth more than a typical annual salary increase. Taking advantage of preferential rate offers (for direct deposit, credit card usage, auto-debits) is genuinely worth this much.

Try entering the two rates alternately in the 'Annual Interest Rate (%)' field and just compare the 'Total Interest' numbers. The 'Repayment Method Comparison' table always calculates all three methods under the same conditions, so if you change the rate, all three rows will update simultaneously.

Making Extra Payments · Prepayment Penalties

The effect of the 'Extra Monthly Payment' field is bigger than you might think. Any extra amount you pay goes directly toward the principal, which eliminates all future interest that would have accrued on that portion.

If you pay an extra 200,000 won per month on a 100 million won, 3.5%, 30-year Equal Installment loan, your 360 payments will be completed in 205. You finish about 12 years and 9 months earlier, and the total interest drops from 61.66 million won to 32.98 million won, saving you about 28.68 million won.

Click 'Save Schedule CSV' to open the payment-by-payment breakdown of principal, interest, and balance in Excel. If you create a cumulative sum of the principal column, you can immediately see when you'll have paid off half the principal. For Equal Installment loans, you'll find that point comes much later than you might expect.

However, in reality, you may face prepayment penalties. These are typically charged within the first 3 years of the loan. The rate varies by product but is often around 0.5-1.5% of the remaining balance, decreasing proportionally with the time remaining. It's common for the penalty to be waived after 3 years. This calculator does not account for these fees, so if you plan to make extra payments, check the prepayment penalty clause in your loan agreement first. Some products also allow for a certain amount of penalty-free prepayment each year.

What This Calculator Assumes — Real Loans Vary by Product

The numbers here are based on a standard calculation assuming a fixed interest rate, monthly compounding, and no fees. While textbook-correct, they won't match the repayment schedule from your bank down to the last won. That's because the following factors vary by product:

Variable Interest Rate — If the rate changes (e.g., every 6 or 12 months), the remaining payments are recalculated from that point. This calculator assumes a fixed rate for the entire term.
Daily Interest Calculation — In practice, many products calculate interest based on the actual number of days in a month (30 vs. 31), so the interest amount can vary slightly between payments.
First Installment — The number of days between the loan disbursement date and the first payment date often differs, so the first month's payment amount is frequently different.
Incidental Costs — Stamp duty, mortgage setup fees, and guarantee fees are not included in this calculation.
Limits & Regulations — Regulations like DSR (Debt Service Ratio) and LTV (Loan-to-Value) may prevent you from borrowing the amount you want, and the loan limit can also vary based on the repayment method. Confirm your actual loan limit with your lender.

This tool is for reference only, to help you understand the differences and scale of various repayment methods. If you are about to sign a contract, always confirm the details with the repayment schedule provided by your bank. The amounts and rates you enter are not sent to the server.

Frequently asked questions

Which is better: Equal Installment or Equal Principal?

Equal Principal repayment always results in less total interest because you pay down the principal faster. However, its initial payments are higher. Equal Installment offers a fixed, predictable monthly payment, which is easier to budget.

How does making an extra monthly payment help?

Any extra amount paid goes directly toward the principal. This saves all future interest on that amount and shortens the loan term. The calculator shows exactly how many months you'll finish earlier and the total interest saved.

Why are these results different from my bank's figures?

This tool is a reference calculator assuming a fixed rate, monthly compounding, and no fees. Banks may use variable rates, daily interest calculations, or add fees (like prepayment penalties), which will alter the final numbers.

Is my loan information sent to your server?

No. All calculations are performed entirely within your browser. The loan amount, interest rate, and any other data you enter are never sent to or stored on our servers, ensuring your financial information remains private.