Mortgage Calculator
Equal Payment / Equal Principal — instant monthly & interest
Principal vs Interest
Monthly Payment Trend (principal + interest)
Amortization Schedule
| Period | Date | Payment | Principal | Interest | Balance |
|---|
Mortgage Calculator — Complete Guide
This calculator estimates the monthly payment and total interest of a home loan. It covers commercial loans, provident-fund loans and combined loans, and lets you compare the two most common repayment methods: equal payment and equal principal.
What this calculator does
Enter the loan amount, the annual interest rate, the term in years and a start date, then choose a repayment method. The tool produces a monthly payment figure, the total amount repaid, the total interest, the interest-to-total ratio, and a full amortization schedule you can page through month by month.
The formula
For the equal-payment method (constant monthly instalments) the payment is:
i = annual rate ÷ 12 n = years × 12
For the equal-principal method the principal repaid each month is fixed at P ÷ n, while interest is the outstanding balance times i, so the payment starts high and declines every month.
A worked example
Take a loan of ¥1,000,000 at 3.9% per year over 20 years using equal payment. The monthly rate is i = 0.039 ÷ 12 = 0.00325 and the number of periods is n = 240. Raising (1 + i) to the 240th power gives about 2.1787, so substituting into the formula yields a monthly payment of roughly ¥6,007. Across 240 months the total repaid is about ¥1,441,700, of which roughly ¥441,700 is interest — an interest ratio near 30.6%. Switching to equal principal would raise the first payment but cut total interest.
| Item | Equal Payment | Equal Principal |
|---|---|---|
| First month | ≈ ¥6,007 | Highest, then falls |
| Payment shape | Constant | Declining |
| Total interest | Higher | Lower |
PITI, terms and edge cases
- PITI stands for principal, interest, taxes and insurance. This calculator models principal and interest only; add property tax, home insurance and any mortgage insurance separately for a true monthly cost.
- A longer term lowers the monthly payment but increases the interest paid over the life of the loan.
- Equal payment keeps cash flow predictable; equal principal saves interest but front-loads the cost.
- Combined loans sum the commercial and provident-fund components, each with its own rate.
- Rates and results are estimates for planning, not a bank quote.
Use the schedule to see how much of each early payment is interest, which is often the most eye-opening part of a long mortgage.
房贷计算器完整使用指南
房贷计算器用于估算住房贷款的每月月供与总利息。它支持商业贷款、公积金贷款和组合贷款，并可对比两种最常见的还款方式：等额本息与等额本金。
这个计算器能做什么
输入贷款金额、年利率、贷款年限与开始日期，再选择还款方式，工具会给出月供、还款总额、支付利息、利息占比，并生成一份可按月翻页查看的完整摊还明细表。
计算公式
等额本息（每月还款额固定）的月供公式为：
月利率 = 年利率 ÷ 12 期数 = 年限 × 12
等额本金方式下，每月偿还的本金固定为“贷款本金 ÷ 期数”，利息按剩余本金乘以月利率计算，因此月供逐月递减，前期还款压力较大。
算例演示
以贷款 100 万元、年利率 3.9%、期限 20 年、等额本息为例。月利率 = 0.039 ÷ 12 = 0.00325，期数 = 240。(1+月利率) 的 240 次方约为 2.1787，代入公式可得月供约 6,007 元。240 期累计还款约 1,441,700 元，其中利息约 441,700 元，利息占比接近 30.6%。若改用等额本金，首月月供会更高，但总利息更低。
| 项目 | 等额本息 | 等额本金 |
|---|---|---|
| 首月月供 | 约 6,007 元 | 最高，之后递减 |
| 月供走势 | 固定不变 | 逐月递减 |
| 总利息 | 较高 | 较低 |
PITI、年限与常见问题
- PITI 指本金、利息、税费与保险。本计算器只涵盖本金与利息，房产税、房屋保险以及可能的房贷保险需另行计入，才能得到真实的月度支出。
- 贷款年限越长，月供越低，但整个贷款期内支付的利息越高。
- 等额本息现金流稳定、便于规划；等额本金更省利息，但前期还款压力更大。
- 组合贷款会把商业贷款与公积金贷款两部分相加，各自使用对应的利率。
- 利率与结果均为规划参考，不代表银行最终审批结果。
借助摊还明细表，可以清楚看到早期每期还款中利息所占的比例，这往往是长期房贷中最值得关注的细节。
Frequently Asked Questions
What is the difference between equal payment and equal principal?
Equal payment keeps monthly payments constant but front-loads interest; equal principal pays more in the early months but costs less total interest overall.
What affects my monthly payment?
Loan amount, annual interest rate, term length and repayment method. A longer term lowers monthly payments but increases total interest.
Does this include property tax and insurance?
No — it covers principal and interest only. Add property tax, home insurance and PMI separately for your true monthly cost.
Last reviewed: October 5, 2026 · How we calculate · Sources: IRS, CFPB, CDC, NIH and others