房貸計算器

Overview

A mortgage payment calculator estimates the monthly cost of a home loan from the loan amount, interest rate, and term. Seeing the payment and the total interest over 15, 20, or 30 years helps you judge how much house you can afford and how term length changes the lifetime cost. The calculation happens locally in your browser.

How to Use (Step by Step)

1. 1

   Enter the loan amount

   Home price minus your down payment.

2. 2

   Add the rate and term

   Use the annual rate and the term in years (the tool converts to months).

3. 3

   Check principal vs interest

   Note how much of the total you pay is interest, especially on longer terms.

How It Works

The core principal-and-interest payment uses the amortization formula payment = P · r · (1+r)^n / ((1+r)^n − 1), where P is the loan amount, r is the monthly interest rate, and n is the number of monthly payments. Early in the loan most of each payment is interest; over time the balance falls and more goes to principal. Property tax, insurance, and HOA dues are separate and add to the true monthly housing cost.

When to Use This

Comparing a 15-year and a 30-year mortgage to weigh lower total interest against a higher monthly payment. Estimating how a rate change affects affordability. Setting a price range before house-hunting.

Frequently Asked Questions