finance2026-10-027 min readCalcZen Financial Engineering Lab
Loan Repayment Guide: Amortizing vs. Equal Principal vs. Bullet Repayment
A comparative financial guide analyzing amortized equal installments, straight equal principal reduction, and interest-only bullet loans.
1. Core Repayment Paradigms
The chosen loan repayment structure dictates total cumulative borrowing costs and monthly cash flow obligations. Standard methods encompass equal installments, equal principal reduction, and interest-only bullet loans.
2. Amortized Equal Installment Mechanics
Equal installment amortization keeps monthly payment totals identical. Initially, interest dominates the payment structure; over time, the principal share grows as the outstanding debt shrinks.
3. Equal Principal Reduction: Minimizing Interest
Equal principal divides the initial debt evenly across all term months, assessing interest strictly on the diminishing balance. This structure minimizes total interest paid across the entire loan lifespan.
4. Interest-Only Bullet Loans: Pros & Hazards
Bullet loans demand interest-only payments throughout the loan term, followed by a full balloon principal payment at maturity. While providing minimum immediate burden, total interest paid is maximized.
5. Quantitative Comparison on 100M KRW Loan
On a 100M KRW loan at 4.5% over 36 months:
- Equal Principal costs 6.94M KRW total interest.
- Equal Installment costs 7.09M KRW total interest.
- Bullet repayment costs 13.50M KRW total interest (nearly double).
Frequently Asked Questions
Q. What is the optimal strategy if there is zero prepayment penalty?
Choose equal installments for budgetary stability, but make voluntary principal prepayments whenever excess cash is available to curtail lifetime interest charges.