Understanding your mortgage payment
The number that matters isn’t the loan amount or even the interest rate on its own — it’s what leaves your bank account every month, and what the house ends up costing you in total. A mortgage payment is more than principal and interest, and the “extra” pieces add up fast.
The principal & interest formula
M = P · r(1 + r)n ÷ ((1 + r)n − 1)
where P = loan amount, r = monthly rate (APR ÷ 12), and n = number of monthly payments. Taxes, insurance, PMI, and HOA dues are added on top to get your real monthly cost.
What makes this calculator different
- The whole payment, not half of it. Property tax, insurance, PMI, and HOA are shown alongside principal and interest, so the monthly figure is one you can actually budget around.
- Fixed periods that revert. Model an introductory fixed rate that switches to a different rate later — the payment is recalculated at the switch, just like your lender does, and the higher rate is reflected in your total interest.
- PMI that drops off. We model private mortgage insurance ending automatically at 20% equity, and tell you when and how much it costs in the meantime.
- Extra-payment impact. See exactly how many years and how many dollars of interest an extra monthly payment saves you.
- Full transparency. Every year of the loan is laid out in an exportable amortization table, and every input is yours to change.
Frequently asked questions
What’s included in a monthly mortgage payment?+
Lenders call it PITI: Principal, Interest, Taxes, and Insurance. Many buyers only budget for principal and interest and are surprised when escrow for property tax and homeowner’s insurance — plus PMI and any HOA dues — pushes the real payment hundreds of dollars higher. This calculator shows the full payment, broken down piece by piece.
How is the monthly payment calculated?+
The principal-and-interest portion uses the standard amortization formula M = P · r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan amount, r is the monthly interest rate, and n is the number of monthly payments. Taxes, insurance, PMI, and HOA are added on top to give your true monthly cost.
What is PMI and when does it go away?+
Private mortgage insurance protects the lender when you put down less than 20%. It’s an extra monthly cost that buys you nothing. The good news: it isn’t forever. This tool drops PMI automatically once your loan balance falls to 80% of the home’s value, and shows you roughly when that happens and how much PMI costs you in total.
Should I choose a 15-year or 30-year mortgage?+
A 15-year loan has higher monthly payments but a lower rate and dramatically less total interest. A 30-year loan is more affordable month to month but can cost roughly twice as much interest over its life. Try both terms here and compare the “total interest” figure — the difference is often eye-opening.
What happens when my fixed-rate period ends?+
Many mortgages fix the interest rate for an introductory period — often 2, 3, or 5 years — and then revert to a higher variable or standard rate for the rest of the term. When that happens, the lender recalculates your payment by re-amortizing the remaining balance over the remaining term at the new rate. Enter your fixed period and the rate you expect afterwards, and this calculator shows both payments and folds the higher rate into your total interest, so you’re not blindsided when the introductory deal ends.
Do extra payments really make a difference?+
Enormously. Because early payments are mostly interest, every extra dollar of principal you pay early avoids years of future interest. Enter an extra monthly amount to see how many years it shaves off and how much interest it saves — frequently tens of thousands of dollars.
Disclaimer: This calculator is for educational purposes only. Actual rates, taxes, insurance, and PMI vary by lender, location, and credit profile, and are estimated here. It is not financial or lending advice. Confirm all figures with a qualified mortgage professional.