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Free mortgage calculator — runs in your browser
Mortgage Calculator with Extra Payments & Amortization Schedule
This mortgage calculator is a free online tool that computes your monthly payment with taxes, insurance, PMI and HOA fees, models extra monthly, yearly and one-time payments, and builds a full amortization schedule — entirely in your browser, with no sign-up, no lead forms and no data sent to any server.
100% private — your numbers never leave this page
Your monthly payment
$0/ month
Loan amount
—
Total interest
—
Payoff date
—
Total cost of loan
—
With your extra payments
Interest saved
—
Time saved
—
New payoff
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Loan balance over time
Amortization schedule
Period
Principal
Interest
Extra
Balance
How to use this mortgage calculator
1
Enter your loan
Type the home price, down payment, loan term and interest rate. Taxes, insurance, PMI and HOA are optional but make the monthly number realistic.
2
Add extra payments
Try an extra monthly amount, one extra payment each year, or a one-time lump sum. Results update instantly as you type.
3
Read the schedule
Check your payoff date, interest saved and the year-by-year amortization table — then download the full monthly schedule as a CSV for Excel or Google Sheets.
How the mortgage payment formula works
Fixed-rate mortgages use the standard amortization formula. Your monthly principal-and-interest payment is:
M = P × r(1 + r)n / ((1 + r)n − 1)
where P is the loan amount (home price minus down payment), r is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments (years × 12). For a $320,000 loan at 6.5% over 30 years that works out to about $2,023 per month before taxes and insurance.
Each month, interest is charged on the remaining balance; the rest of your payment reduces principal. That is why early payments are mostly interest and the last ones are almost all principal — the amortization schedule above shows the exact split for every payment.
How extra payments save you money
On a fixed-rate mortgage, every extra dollar you pay goes straight to principal. A smaller balance means less interest accrues each month, so more of every following regular payment also goes to principal — the savings compound for the whole life of the loan.
Extra monthly payment. Adding $200/month to a $320,000, 30-year loan at 6.5% pays it off about 6½ years early and saves over $100,000 in interest.
One extra payment a year. A 13th payment annually (what biweekly payment plans effectively do) typically cuts 4–6 years off a 30-year term.
One-time lump sum. A bonus or tax refund applied early in the loan saves far more than the same amount applied late, because it stops decades of interest on that principal.
Extra payments never lower your required monthly payment — they shorten the loan. Check that your lender applies extra amounts to principal (not to next month's payment) and confirm there is no prepayment penalty; most US mortgages have none.
PMI, property taxes and insurance in your payment
Lenders quote the principal-and-interest payment, but what you actually send each month usually includes escrow items. This calculator itemizes all of them:
Property tax — set by your county, commonly 0.5%–2.5% of home value per year, paid monthly into escrow.
Homeowners insurance — required by lenders; the US average is roughly $1,500–$2,500 per year depending on the state.
PMI (private mortgage insurance) — charged when your down payment is below 20%, typically 0.3%–1.5% of the loan amount per year. It cancels automatically at 78% loan-to-value (you can request removal at 80%), and this calculator drops it from your payment at exactly that point.
HOA fees — for condos and many planned communities; paid to the association, not the lender.
Because all of the math runs locally in your browser, you can test scenarios freely — refinance rates, 15 vs 30-year terms, bigger down payments — without creating an account or receiving sales calls. Nothing you type is uploaded, stored or shared.
Mortgage calculator FAQ
How is the monthly mortgage payment calculated?
The principal-and-interest part uses the amortization formula M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan amount, r the monthly rate and n the number of payments. Property tax, insurance, PMI and HOA are added on top to show your full monthly housing cost.
Do extra payments lower my monthly payment or shorten the loan term?
They shorten the term. With a fixed-rate mortgage your required payment stays the same; extra money reduces principal, so the loan ends earlier and total interest drops. The green panel above shows exactly how much time and interest you save.
When does PMI go away?
By the Homeowners Protection Act, PMI must be cancelled automatically when your balance reaches 78% of the original home value, and you may request cancellation at 80%. This calculator removes PMI from your payment as soon as the balance hits 80% loan-to-value.
How much can one extra payment a year save?
Typically 4–6 years and tens of thousands of dollars on a 30-year loan, depending on the rate. Enter your own numbers in the "Extra yearly" field to see the exact savings and your new payoff date.
Is this mortgage calculator free and private?
Yes — completely free, no sign-up, no lead forms, no lender calls. Every calculation runs locally in your browser with JavaScript; the numbers you enter are never sent to a server.
What is an amortization schedule?
A payment-by-payment table showing how each payment splits between interest and principal and what balance remains. View it yearly or monthly above, and download the full schedule as a CSV for Excel or Google Sheets.
Disclaimer: this calculator provides estimates for educational purposes only and is not financial advice or a loan offer. Actual payments depend on your lender's terms, exact closing date, escrow rules, and local taxes and insurance. Always confirm figures with your lender before making decisions.