Mortgage Calculator
Calculate monthly payments, total interest. Supports commercial loans, provident fund loans, and combined loans
What is a Mortgage Calculator?
A mortgage calculator is an online home loan calculation tool designed specifically for homebuyers. It quickly and accurately calculates mortgage repayment amounts. Whether you're a first-time buyer or looking to upgrade, this tool helps you fully understand your loan repayment situation and make informed homebuying decisions. Core Features: Monthly Payment Calculation, Interest Statistics, Payment Details, Multi-Plan Comparison. Supported Loan Types: Commercial Loan (bank-provided, higher rates but flexible amounts), Provident Fund Loan (favorable rates but limited amounts), Combined Loan (balancing rate advantages and loan amounts). Supported Repayment Methods: Equal Principal & Interest (fixed monthly payments), Equal Principal (same principal each month, decreasing interest). This calculator uses standard bank calculation formulas for accurate and reliable results. All calculations are performed locally in your browser to protect your privacy.
How to Use
How to use
- Select loan type: commercial, provident fund, or combined loan
- Select repayment method: equal principal & interest or equal principal
- Enter loan amount (unit: 10,000)
- Enter loan term (typically 1-30 years)
- Enter or use default interest rate (consult your bank for current rates)
- Click 'Calculate' to view results
- Click 'Payment Schedule' to view period-by-period repayment plan
Practical Tips
- Try different loan terms to compare monthly payment pressure against total interest cost before choosing a plan.
- Enter the rate actually approved by the bank; small rate differences can create large long-term interest changes.
- Use the payment schedule for early repayment planning, but confirm penalty rules and recalculation methods with the lender.
Use Cases
Technical Principle
The two core mortgage formulas correspond to the two repayment methods. Equal principal & interest keeps the monthly payment fixed: payment = principal x monthly_rate x (1 + monthly_rate)^N / ((1 + monthly_rate)^N - 1), where N is the total number of months and monthly_rate = annual_rate / 12. Early on, interest dominates each payment; later, principal takes over. Equal principal splits the principal evenly: monthly_principal = principal / N, monthly_interest = remaining_principal x monthly_rate, monthly_payment = monthly_principal + monthly_interest, so the payment is high at first and decreases month by month. At the same principal, rate, and term, equal principal saves 10%-15% on total interest compared to equal P&I, but the early monthly payment is 20%-30% higher, which is harder on cash flow. Choosing equal principal is fundamentally a trade-off: pay more now, save more over 30 years. Commercial loan rates are anchored to the LPR (Loan Prime Rate) published by the National Interbank Funding Center, with banks adding their own spread based on first/second home, credit, and region. The rate is repriced periodically per the contract (commonly yearly) following LPR. Provident fund rates are set by the housing provident fund center, usually lower than commercial, but with a cap. A combined loan is simply the two plans computed separately and added together - it gets you a lower rate while breaking through the provident fund cap. For early repayment, banks usually offer two options: 'reduce the monthly payment, keep the term' lowers the monthly burden immediately; 'shorten the term, keep the payment' saves more total interest but leaves the cash flow unchanged. The actual savings depend on the remaining principal, remaining term, and current rate, and must be run through the calculator - never estimated by feel.
- Equal P&I: payment = principal x monthly_rate x (1+monthly_rate)^N / ((1+monthly_rate)^N - 1); the monthly amount is fixed but interest dominates early on.
- Equal principal: monthly_principal = principal / N, payment = monthly_principal + remaining_principal x monthly_rate; the monthly amount decreases over time.
- At the same conditions, equal principal saves 10%-15% on total interest but the early monthly payment is 20%-30% higher, demanding stronger cash flow.
- Commercial rates are LPR + spread and reprice periodically with LPR; provident fund rates are set by the provident fund center.
- Combined loan = provident fund (use up the cap) + commercial (fill the gap); the blended rate is lower than pure commercial.
- Two early-repayment options: 'reduce payment' eases cash flow immediately, 'shorten term' saves more interest - use the calculator to run both.
- Calculations are for plan comparison only; the final payment, rate, and schedule are determined by the bank's system and the loan contract.
Examples
Equal P&I: 1,000,000 CNY, 30 years, 4.2%
Inputs:
Principal P = 1,000,000 CNY
Annual rate = 4.2% -> monthly r = 0.042 / 12 = 0.0035
Term = 30 years -> N = 360 months
Formula:
M = P * r * (1+r)^N / ((1+r)^N - 1)
= 1,000,000 * 0.0035 * (1.0035)^360 / ((1.0035)^360 - 1)
= 1,000,000 * 0.0035 * 3.5174 / (3.5174 - 1)
= 12,311 / 2.5174
= 4,890.84 CNY / month (fixed for 360 months)
Result:
Monthly payment: 4,890.84 CNY (constant)
Total payment: 4,890.84 * 360 = 1,760,701 CNY
Total interest: 760,701 CNY (~76% of principal)
First month split: interest 3,500 + principal 1,390.84
Year 1 paid principal: ~16,800 (interest-heavy start)
Year 20 paid principal: ~2,700 / month (principal-heavy end)Equal Principal: same loan, lower total interest
Inputs: P = 1,000,000 CNY, 30 years, 4.2%
Formulas:
monthly_principal = P / N = 1,000,000 / 360 = 2,777.78 CNY (constant)
monthly_interest = remaining_principal * r
monthly_payment = monthly_principal + monthly_interest
Result:
Month 1: interest 3,500.00 + principal 2,777.78 = payment 6,277.78
Month 60: interest 2,402.50 + principal 2,777.78 = payment 5,180.28
Month 180: interest 1,266.39 + principal 2,777.78 = payment 4,044.17
Month 360: interest 9.72 + principal 2,777.78 = payment 2,787.50
Total interest: 630,972 CNY (130K less than equal P&I)
First-month payment 6,277.78 is 28% higher than equal P&I 4,890.84,
which is the real cash-flow hurdle for the first year.Combined loan: fund cap + commercial gap
Inputs: 600,000 CNY provident fund at 2.85% + 400,000 CNY commercial at 4.2%
Term: 30 years, equal P&I for both segments
Fund segment (2.85%):
r = 0.0285/12 = 0.002375, N = 360
M = 600,000 * 0.002375 * (1.002375)^360 / ((1.002375)^360 - 1)
= 2,481.31 CNY / month
Total interest: 293,272 CNY
Commercial segment (4.2%):
M = 400,000 * 0.0035 * 3.5174 / 2.5174 = 1,956.34 CNY / month
Total interest: 304,282 CNY
Combined:
Monthly payment: 4,437.65 CNY (vs 4,890.84 for pure commercial 1M)
Total interest: 597,554 CNY (vs 760,701 for pure commercial 1M)
Interest saved: 163,147 CNY by using the fund cap first.Early repayment: shorten term vs reduce payment
Inputs: 1,000,000 CNY equal P&I, 30 years at 4.2%, after 5 years (60 months paid),
prepay 200,000 CNY
State at month 60:
Remaining principal: ~946,300 CNY
Remaining term: 300 months
Current monthly: 4,890.84
Option A: shorten the term, keep the payment 4,890.84
New payoff in ~212 months (i.e. ~17.6 years from now)
Interest saved: ~190,000 CNY (most of the remaining interest is gone)
Option B: reduce the monthly payment, keep the term at 300 months
New monthly = 946,300 * 0.0035 * 1.0035^300 / (1.0035^300 - 1) = ~3,867 CNY
Interest saved: ~43,000 CNY (only the principal share shrinks; the term is the same)
Cash-flow impact: option B frees ~1,000 CNY / month, option A frees nothing
but deletes ~7.4 years of payments. Pick by whether the budget relief is
worth the lost interest savings.FAQ
Which loan types does the calculator support?
Equal-payment-amortizing (等额本息) where every monthly payment is the same, and equal-principal (等额本金) where you pay a fixed principal each month plus a declining interest portion. Some pages also model interest-only and graduated payments. Pick the type your lender actually uses.
What's the formula behind equal-payment loans?
Monthly payment M = P × r × (1+r)^n / ((1+r)^n − 1), where P is principal, r is monthly interest rate (annual rate / 12), and n is number of payments (years × 12). Total interest = M × n − P. The calculator shows the amortization schedule month by month.
Equal-payment vs. equal-principal - which is cheaper?
Equal-principal pays less total interest because the principal balance falls faster, but its early monthly payments are larger. Equal-payment smooths the cash flow at the cost of slightly more total interest. Most homebuyers choose equal-payment for budgeting predictability.
How is variable-rate (LPR) handled?
The calculator uses the rate you input as a constant. For variable mortgages tied to LPR (Loan Prime Rate) or other reference rates, real payments will adjust at each repricing date. Re-run the calculator with the new rate after each adjustment to see updated remaining-payment numbers.
Should I make extra payments?
If your loan has no prepayment penalty, extra payments toward principal save interest proportionally - on a long mortgage the savings are substantial. Check your loan agreement first; some variable-rate or government-backed loans charge prepayment fees during the first few years.
Are taxes, insurance, and fees included?
The base calculation covers principal and interest only. Property tax, home insurance, HOA fees, mortgage insurance (PMI), and origination/closing costs are not included by default. If the page exposes a 'monthly costs' field, add them there for a true monthly housing cost.
Is my financial information uploaded?
No. The calculation runs entirely in your browser. Loan amount, rate, and term are not saved or transmitted.