Home Mortgage Calculator
Estimate monthly mortgage payments, total interest, and loan costs for a home purchase.
What This Mortgage Calculator Does
This calculator estimates your monthly mortgage payment based on the home price, down payment, loan term, and interest rate. It also shows the total interest you will pay over the life of the loan and the total cost of the home. The goal is to give you a realistic picture of what a specific property might cost you each month before you commit to a loan.
How Your Monthly Payment Is Calculated
The calculator uses the standard amortization formula for fixed-rate mortgages. Your monthly payment is determined by three main factors:
- Loan principal – The home price minus your down payment.
- Interest rate – The annual rate your lender charges, divided by 12 for the monthly rate.
- Loan term – The number of monthly payments (e.g., 360 payments for a 30-year loan).
The formula calculates a fixed payment that pays off both the principal and interest over the term. Early payments go mostly toward interest; later payments go mostly toward principal. This is called amortization.
Important assumption: This calculator does not include property taxes, homeowners insurance, or private mortgage insurance (PMI). Those costs vary by location and lender and can significantly increase your actual monthly payment.
How to Use the Calculator
- Enter the home price – The total purchase price of the property.
- Enter your down payment – You can enter a dollar amount or a percentage of the home price.
- Choose a loan term – Common options are 15 years and 30 years.
- Enter the interest rate – Use the rate you have been quoted or a current market rate.
The calculator updates instantly. Adjust any input to see how it changes your monthly payment and total interest.
Example Calculation
Consider a home priced at $400,000 with a 20% down payment ($80,000). The loan amount is $320,000. With a 30-year term and a 6.5% interest rate:
- Monthly payment: Approximately $2,023
- Total interest paid: Approximately $408,000
- Total cost of the home: Approximately $808,000 (including the down payment)
This example shows how much interest accumulates over a 30-year term. A shorter term or lower rate would reduce the total interest significantly.
Understanding Your Results
The results show three key numbers:
- Monthly payment – Your principal and interest payment each month. This is the base cost of the loan.
- Total interest – The total amount of interest you will pay over the full loan term. This number is often larger than expected.
- Total cost – The sum of your down payment, all principal payments, and all interest payments. This is the true cost of buying the home with this loan.
Use these numbers to compare different loan scenarios. A lower monthly payment often means more total interest over time. A higher down payment reduces both.
Common Mistakes When Using a Mortgage Calculator
- Ignoring taxes and insurance. Property taxes and homeowners insurance can add hundreds of dollars to your monthly payment. Check local rates and include them in your budget.
- Forgetting PMI. If your down payment is less than 20%, lenders typically require private mortgage insurance. This adds to your monthly cost.
- Using an unrealistic interest rate. Your actual rate depends on your credit score, loan type, and current market conditions. Use a rate you have been pre-approved for, not a best-case estimate.
- Not considering closing costs. Closing costs (typically 2% to 5% of the loan amount) are paid upfront and are not reflected in this calculator.
Limitations of This Calculator
- It only calculates principal and interest. It does not include taxes, insurance, HOA fees, or PMI.
- It assumes a fixed interest rate for the entire loan term. Adjustable-rate mortgages (ARMs) are not supported.
- It does not account for extra payments. Making additional principal payments would reduce total interest and shorten the loan term.
- It assumes the loan starts immediately and payments are made on time every month.
Use this calculator as a starting point for budgeting. For a complete picture, consult a lender who can provide a detailed loan estimate.
Practical Use Cases
- Comparing loan terms: See how a 15-year mortgage compares to a 30-year mortgage in terms of monthly payment and total interest.
- Evaluating down payment options: Test different down payment amounts to see how they affect your monthly payment and whether you can avoid PMI.
- Budgeting for a home purchase: Determine the maximum home price you can afford based on your target monthly payment.
- Rate shopping: Compare offers from different lenders by entering their quoted rates and seeing the long-term cost difference.
Frequently Asked Questions
Does this calculator include property taxes and insurance?
No. This calculator only estimates principal and interest. Property taxes, homeowners insurance, and PMI are not included. You will need to add those costs separately to get your full monthly housing payment.
What is a good down payment for a home?
A 20% down payment is common because it eliminates the need for PMI and reduces your loan amount. However, many loans allow down payments as low as 3% to 5%. A smaller down payment means a higher monthly payment and more total interest.
Should I choose a 15-year or 30-year mortgage?
A 30-year mortgage has a lower monthly payment but much higher total interest. A 15-year mortgage has a higher monthly payment but significantly less total interest. Choose based on your monthly budget and long-term financial goals.
How accurate is this calculator?
The calculator is mathematically accurate for fixed-rate amortization. However, the result is only as accurate as the inputs you provide. Actual loan terms, fees, and rates from a lender may differ.
Can I use this calculator for an adjustable-rate mortgage (ARM)?
No. This calculator assumes a fixed interest rate for the entire loan term. ARMs have rates that change after an initial period, which this tool does not account for.