How is your monthly mortgage payment calculated?
Your principal-and-interest payment comes from the standard amortization formula: the loan amount, the monthly interest rate, and the number of payments determine a fixed monthly amount that fully pays the loan off by the end of the term. Early on, most of each payment is interest; over time the split flips toward principal. That shift is what the chart and the year-by-year schedule above make visible.
But principal and interest is only part of what you will actually pay each month. Lenders collect property taxes and homeowners insurance into escrow, add PMI when your down payment is below 20%, and your HOA bills you separately. This calculator shows every component, because the gap between "the payment in the ad" and "the payment you write a check for" is routinely $500 or more.
What each input means
- Home price & down payment — the difference is your loan amount. Use the %/$ toggle to think in either unit; the hint below the field always shows the other one.
- Interest rate — your quoted annual rate (not APR). APR includes fees and is useful for comparing offers, but monthly payments are computed from the note rate.
- Property tax — entered as a percent of home value per year. The U.S. average effective rate is roughly 1.1%, but real rates run from about 0.3% (Hawaii) to over 2% (New Jersey, Illinois) — check your county figure.
- Home insurance — annual premium. Nationwide averages run around $1,800–$2,400/year but vary widely by state and home.
- PMI rate — applied automatically only while your loan-to-value is above the cancellation threshold (see below). 0.5%/year is a typical mid-range figure.
- Extra payment — additional principal added to every monthly payment. The results show exactly how many months and dollars it saves.
How PMI works in this calculator
If your down payment is under 20%, most conventional lenders require private mortgage insurance. We charge your PMI rate on the loan amount, monthly, and then remove it automatically at the point your balance is scheduled to reach 78% of the original home value — the auto-termination rule set by the federal Homeowners Protection Act. You can also request cancellation earlier, at 80%, or reach the threshold faster by making extra payments; the schedule above reflects extra payments in the PMI cutoff.
Do extra payments really make a difference?
Yes — and the effect compounds. Every extra dollar reduces the balance that all future interest is computed on. On a $200,000 loan at 6% over 30 years, adding $100 a month cuts the payoff time by 5 years 5 months and saves roughly $49,000 of interest; adding $250 a month saves over $95,000. Two cautions: make sure your servicer applies extras to principal (not next month's payment), and confirm your loan has no prepayment penalty — most modern U.S. mortgages do not.
Frequently asked questions
How is a monthly mortgage payment calculated?
The principal-and-interest part uses the standard amortization formula M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is your loan amount, r is your monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments. Your real monthly bill adds property taxes, homeowners insurance, PMI if you put less than 20% down, and any HOA dues on top of that number.
What does PITI mean?
PITI stands for Principal, Interest, Taxes, and Insurance — the four parts of a typical mortgage payment. Principal pays down the loan, interest is the lender’s charge, and taxes and insurance are usually collected monthly into an escrow account and paid by your servicer.
How much is PMI, and when does it go away?
Private mortgage insurance typically costs about 0.3%–1.5% of the loan amount per year, charged monthly, and applies when your down payment is under 20%. Under the federal Homeowners Protection Act it terminates automatically once your balance reaches 78% of the home’s original value, and you can request cancellation at 80%. This calculator applies PMI at your chosen rate and drops it at the 78% threshold.
What happens if I pay an extra $100 a month?
Every extra dollar goes straight to principal, so future interest is charged on a smaller balance. For example, on a $200,000 loan at 6% for 30 years, an extra $100/month pays the loan off 5 years and 5 months early and saves about $49,000 in interest. Enter any extra amount above to see your own numbers and the before/after comparison on the chart.
Why is my real payment higher than principal and interest?
Advertised payment examples often show only principal and interest. Escrowed property taxes and homeowners insurance commonly add several hundred dollars a month, and PMI or HOA dues add more. That is why this calculator shows the full breakdown instead of a single teaser number.
Is it better to put 20% down?
Reaching 20% down avoids PMI and lowers your monthly payment, but it is not always the right call — draining savings to hit 20% can leave you without an emergency fund. Try both scenarios above and compare the total monthly payments; the difference is mostly the PMI line.
Does this calculator include HOA fees?
Yes. Enter your monthly homeowners-association dues in the HOA field and they are added to the total monthly payment. HOA fees are not part of your loan and never go away as the loan is paid down.
What interest rate should I enter?
Use a current quote from a lender if you have one. If not, enter the average 30-year fixed rate you see in the news, then test a half-point above and below it — payment sensitivity to rate is exactly what this tool is for. We intentionally do not auto-fill a "today’s rate" because we would rather show no number than a stale one.
How accurate are these estimates?
The amortization math is exact and verified against published reference values (see our About page for how we test). The estimate quality depends on your inputs: property tax rates vary by county, insurance varies by home and insurer, and your final rate depends on credit and fees. Treat results as a planning estimate, not a lender quote.
All mortgage calculators
Specialized tools for specific decisions — each shares this page's verified math engine approach:
- Home Affordability Calculator — How much house can you afford? Income, debts, and the 28/36 rule turned into a real price range.
- Extra Payment Mortgage Calculator — What paying more each month (or one lump sum) does to your mortgage payoff date and interest.
- Biweekly Mortgage Calculator — Half your payment every two weeks equals 13 payments a year — see the years and interest it removes.
- 15-Year Mortgage Calculator — 15 vs. 30 years side by side: payment difference, interest difference, and equity build.
- FHA Loan Calculator — FHA payment with both MIP charges included — upfront 1.75% and the annual premium, with the 11-year rule.
- VA Loan Calculator — VA payment with the correct funding fee for your down payment and usage — and no PMI.
- Mortgage Payoff Calculator — Pay off your existing mortgage early: extra monthly payments, lump sums, and your new payoff date.
- Refinance Calculator — Find your break-even month and lifetime savings before you refinance.
Disclaimer: This calculator is for educational purposes only and does not constitute financial advice or a loan offer. Actual rates, taxes, insurance, and fees vary. Verify figures with your lender and county before making decisions. See our Terms of Use.