房贷计算器

What is a Mortgage Calculator?

A mortgage calculator estimates your monthly house payment including principal, interest, property taxes, homeowner's insurance, and private mortgage insurance (PMI). Understanding your total housing cost—not just the loan payment—is essential for budgeting and determining how much house you can afford.

The Mortgage Payment Formula

Monthly principal and interest is calculated using:

M = P × [r(1+r)^n] ÷ [(1+r)^n - 1]

Then add monthly amounts for taxes, insurance, and PMI:

Total Payment = Principal & Interest + (Annual Property Tax ÷ 12) + (Annual Insurance ÷ 12) + Monthly PMI

For a $350,000 home with 20% down, 6.5% rate, 30 years: ~$1,771/month P&I + ~$292 taxes + ~$100 insurance = ~$2,163/month total

Understanding Payment Components

• Principal: The portion reducing your loan balance
• Interest: The cost of borrowing (front-loaded in early years)
• Property Tax: Typically 0.5% to 2.5% of home value annually, varies by location
• Homeowner's Insurance: Usually $1,000-$3,000/year for typical homes
• PMI: Required for down payments under 20%, costs 0.3%-1.5% annually
• HOA Fees: Additional monthly fees for condos/planned communities (not included here)

Real-World Mortgage Examples

• $250,000 home, 20% down, 6.5%, 30 years: $1,265/month P&I, ~$1,600 total with taxes/insurance
• $350,000 home, 10% down, 6.5%, 30 years: $1,991/month P&I + $133 PMI, ~$2,500 total
• $450,000 home, 20% down, 6.5%, 15 years: $3,133/month P&I, ~$3,600 total (pays off faster, saves $200K+ interest)
• $500,000 home, 5% down, 7%, 30 years: $3,161/month P&I + $395 PMI, ~$4,000 total

15-Year vs 30-Year Mortgage

On a $280,000 loan at 6.5%:

• 30-year: $1,770/month, $357,000 total interest
• 15-year: $2,441/month, $159,000 total interest
• Savings with 15-year: $198,000 less interest, but $671/month higher payments

How Down Payment Affects Your Mortgage

For a $400,000 home at 6.5%:

• 5% down ($20K): $380,000 loan, ~$2,400/month + PMI (~$317/month)
• 10% down ($40K): $360,000 loan, ~$2,275/month + PMI (~$225/month)
• 20% down ($80K): $320,000 loan, ~$2,023/month, no PMI
• PMI savings: 20% down saves you $225-$317/month until you reach 20% equity

The 28% Rule for Affordability

Financial experts recommend your housing costs (mortgage + taxes + insurance) shouldn't exceed 28% of gross monthly income:

• $60,000 income: Max housing = $1,400/month → ~$225,000 home
• $80,000 income: Max housing = $1,867/month → ~$300,000 home
• $100,000 income: Max housing = $2,333/month → ~$375,000 home
• $120,000 income: Max housing = $2,800/month → ~$450,000 home

Extra Payments Save Thousands

On a $300,000 mortgage at 6.5% for 30 years:

• Standard payments: $1,896/month, $382,000 total interest, paid off in 2055
• +$200/month extra: $100,000 less interest, paid off 7 years early
• +$500/month extra: $175,000 less interest, paid off 13 years early
• One extra payment/year: $75,000 less interest, paid off 5 years early

Related Mortgage Tools

• Amortization Calculator – See your full payment schedule year by year
• Loan Calculator – Compare different loan scenarios
• Compound Interest Calculator – See how your down payment could grow if invested instead
• Paycheck Calculator – Know your take-home pay to budget for housing

About Our Calculations

Our mortgage calculator uses standard amortization formulas used by lenders. We display current average rates from the Federal Reserve (FRED), but your actual rate depends on credit score (typically 740+ for best rates), debt-to-income ratio, loan type (conventional, FHA, VA, USDA), and current market conditions. Tax and insurance estimates are averages—verify local property tax rates and get insurance quotes for accurate planning.