ReckonBoxHow the mortgage calculator works
A mortgage payment is principal and interest plus the costs that ride alongside it: property tax, home insurance, HOA dues, and mortgage insurance if you put down less than 20%. Lenders call the first four PITI and collect the tax and insurance into an escrow account with the loan payment, which is why the figure on your statement is never the one a bare loan calculator returns.
Take the default. A $420,000 home with 10% down leaves a $378,000 loan, and at 6.55% over 30 years the principal and interest come to $2,401.66 a month. Add $385 of property tax, $150 of insurance and $196.88 of mortgage insurance and the real number is $3,133.54. The loan costs $486,598 in interest over the full term, which is more than you borrowed.
The two dates PMI can end, and why they differ
Private mortgage insurance has two termination points in federal law: you may request cancellation when the balance is scheduled to reach 80% of the original value, and the servicer must terminate it automatically at 78%. The Consumer Financial Protection Bureau sets both out, along with a backstop that ends the premium the month after the midpoint of the amortization schedule, which is year 15 on a 30-year loan. All of it applies to single-family principal residences with loans closed on or after 29 July 1999.
On the default loan those dates are 8 years and 9 years 2 months. Fourteen months apart, at $196.88 a month, is $2,756 that belongs to whoever writes the letter.
| Month | Total PMI paid by then | |
|---|---|---|
| You may request cancellation | 96 | $18,703 |
| Servicer must terminate | 110 | $21,459 |
| Charged for the full 30 years | 360 | $70,877 |
That third row is not hypothetical. Of the twelve mortgage calculators we fetched on 21 July 2026, the one ranking first bills PMI in every month of the schedule, including month 360 of a loan that crossed 78% a decade earlier, which overstates the cost of this house by $49,417.
Original value means the lower of the contract price and the purchase appraisal, so a home that has doubled in value does not reach the threshold sooner by right. Both figures also track the scheduled balance, which is why the extra-principal field below changes your payoff date without moving either PMI date by a single month.
What the schedule really looks like
Interest is charged on what you still owe, so early payments are almost entirely interest and the split shifts slowly. Year one on the default loan puts $24,635 toward interest and $4,185 toward the balance, a ratio near six to one. Principal does not overtake interest until year 20.
That is two-thirds of the way through a loan most people expect to be roughly half paid off by the halfway mark. Sell in year seven and you'll have paid $201,739 in principal and interest against a balance that has fallen by $35,943.
Where the numbers come from
The payment uses M = P times r times (1 + r) to the power n, divided by (1 + r) to the power n minus 1, with P the loan amount, r the annual rate divided by 12, and n the number of monthly payments. Property tax is a percentage of the purchase price. PMI is an annual percentage of the original loan amount, charged only while the loan sits above 80% of value, at bands running from roughly 0.375% near 85% loan-to-value up to about 1.03% at 100%.
The interest rate default, 6.55%, is the Freddie Mac Primary Mortgage Market Survey 30-year average for the week of 16 July 2026. Property tax at 1.1% is a rough national placeholder and a poor one for any specific address: county rates vary by more than a factor of five, so replace it with yours.
What this does not decide for you
This calculator prices a mortgage and dates its insurance. It cannot tell you whether to buy, what you can comfortably carry, or which loan to take, and it is not a lending decision or a quote. Escrow amounts change as tax assessments and premiums change. PMI cancellation on request also requires you to be current on payments, to have no junior liens, and to show the value has not fallen. Talk to a licensed mortgage professional about your own file, and to your servicer about the cancellation process in writing.
Frequently asked questions
What is a mortgage calculator? A mortgage calculator estimates the monthly cost of a home loan by combining principal and interest with property tax, home insurance, mortgage insurance and any HOA dues. On a $420,000 home with 10% down at 6.55% over 30 years, the loan is $378,000, principal and interest come to $2,401.66, and the full monthly payment is $3,133.54.
When does PMI go away? Under the Homeowners Protection Act you can ask your servicer to cancel PMI once the balance is scheduled to reach 80% of the original value, and the servicer must terminate it automatically at 78%. On the default loan those dates are 8 years and 9 years 2 months, so asking on time rather than waiting saves about $2,756. Both thresholds use the price you paid, not what the home is worth now.
Does paying extra make PMI end sooner? No, and this catches people out. The two statutory dates run off the scheduled amortization, so overpaying clears the loan years early without moving either date. What extra payments do change is your actual balance, which can support a request for early cancellation based on a new appraisal, at the servicer discretion rather than by right.
What is PITI? PITI is principal, interest, taxes and insurance, the four parts of a typical mortgage payment. Lenders quote it because taxes and insurance are usually collected with the loan payment into an escrow account, so on the default loan the $2,401.66 of principal and interest becomes $3,133.54 once $385 of tax, $150 of insurance and $196.88 of PMI are added.
How much of my payment goes to interest? Most of it, for a long time. On the default 30-year loan, year one puts $24,635 toward interest and only $4,185 toward the balance, and principal does not overtake interest until year 20. That is why the total interest reaches $486,598, more than the loan itself.
What is the mortgage payment formula? The monthly principal and interest is M = P times r times (1 + r) to the power n, divided by (1 + r) to the power n minus 1, where P is the loan amount, r the annual rate divided by 12, and n the number of monthly payments. Taxes, insurance, PMI and HOA are added on top and are not part of that formula.
How much house can I afford at this payment? That works the other way round, from your income and existing debts rather than from a price. The house affordability calculator applies the qualifying ratios lenders use and returns a price, and the debt-to-income calculator shows the ratio those rules are testing.