Mortgage Calculator

How the monthly payment is calculated

A fixed-rate mortgage payment stays the same every month for the life of the loan, but the split between principal and interest inside that payment changes constantly. Lenders use one standard formula — M = P × [r(1+r)^n] / [(1+r)^n − 1] — where P is the loan amount (home price minus down payment), r is the annual interest rate divided by 12, and n is the total number of monthly payments (loan term in years × 12). Every month, interest is charged on whatever balance is left, so the interest portion is largest at the start and shrinks steadily while the principal portion grows to match — this calculator's amortization schedule below makes that shift visible year by year, or month by month.

Worked example

A $400,000 home with 20% down ($80,000), a 6.5% APR interest rate and a 30-year term produces the following, exactly as this calculator computes it:

Home price:                 $400,000
Down payment:                 $80,000 (20%)
Loan amount:                 $320,000
Interest rate:                   6.5% APR
Loan term:                        30 years

Monthly payment (P&I):        $2,022.62
Total interest paid:         $408,142.36
Total cost (loan + down):    $808,142.36
Payoff date:              January 2057 (first payment: January 2027)

Amortization — selected years
Year 1:  principal $3,576.72   interest $20,694.69   balance $316,423.28
Year 15: principal $8,863.94   interest $15,407.48   balance $232,189.25
Year 30: principal $23,438.03  interest $833.39       balance $0.00

Notice how the principal paid in year 30 ($23,438.03) is more than six times what it was in year 1 ($3,576.72), even though the monthly payment itself never changed — that's the amortization curve in action. For the taxes and insurance side of the full PITI picture, Frost Rank's full tools directory covers more calculators as they launch.

How to calculate your mortgage payment

1. 1
   Enter the loan basics

   Fill in home price, down payment, loan term and interest rate.

2. 2
   Add taxes & fees (optional)

   Check "Include property tax, insurance, PMI & HOA" to fold those estimated costs into a full monthly payment figure.

3. 3
   Read your results

   See the monthly payment breakdown, loan amount, total interest, total cost and payoff date update instantly as you type.

4. 4
   Review the amortization schedule

   Switch between the annual and monthly views to see exactly how each payment splits between principal and interest over the life of the loan.

Common use cases

• Estimating a comfortable price range before you start house hunting or talk to a lender.
• Comparing the monthly payment and total interest of a 15-year and a 30-year term.
• Seeing how a bigger down payment changes the monthly payment and whether PMI still applies.
• Checking the figures on a lender's loan estimate against your own calculation.
• Exporting the amortization schedule as a CSV file to plan a budget in a spreadsheet.

Tips and common mistakes

• Use a realistic rate. Advertised rates often assume excellent credit and paid points. Try your quoted rate plus and minus half a percentage point to see how sensitive the payment is.
• Include the other costs. Principal and interest alone understate what you will pay each month; tick the option to add property tax, insurance, PMI and HOA fees. PMI usually applies to a conventional loan with less than 20% down, and you can ask to cancel it once your balance is scheduled to reach 80% of the home's original value.
• Budget for closing costs separately. Fees at closing commonly run to a few percent of the loan amount and are not part of this calculation.
• Keep your paperwork ready. Lenders usually ask self-employed borrowers for proof of income such as tax returns, bank statements and invoices; clear, numbered invoices from the Invoice Generator make that easier. The mortgage calculator guide explains how term, rate and down payment interact.

Frequently asked questions