Finance & Money · 等额本息 · Updated 2026-10-25
What Is Equal Monthly Installment?
Definition
The most common mortgage repayment method: total monthly payment stays fixed while its principal share grows over time. Steady cash flow, but slower principal decline means more total interest.
Formula
M = P × r × (1+r)^n / [(1+r)^n − 1]
Worked Example
On 1M/30y/3.0%, the first payment is 2,500 interest vs 1,716 principal; only by year 20 does principal dominate.
Common Misconception
"Early installments are all interest, so I lose money" - interest always equals remaining principal x monthly rate; the bank charges nothing extra. Higher total interest only reflects slower principal repayment, and prepayment can stop the loss anytime.
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