What a mortgage payment actually contains
The number a lender quotes you — the principal-and-interest payment — is usually the smallest version of the truth. The amount that leaves your bank account each month is PITI plus extras: Principal, Interest, property Taxes, homeowners Insurance, plus HOA dues if the property has an association and PMI if you put less than 20% down. This calculator adds all five so the monthly figure you budget against is the complete one.
Take the default example: a $450,000 home with $90,000 down (exactly 20%) at 6.75% over 30 years. The loan is $360,000 and the principal-and-interest payment works out to $2,334.95. Add property tax at 1.1% of the home value ($412.50 a month), insurance at $1,800 a year ($150 a month), and a $150 HOA, and the real monthly cost is $3,047.45 — about 31% more than the quoted payment. On a $9,000 gross monthly income, that is a 33.9% housing ratio, noticeably above the common 28% guideline, which is exactly the kind of thing worth knowing before falling in love with a listing.
The quiet cost of a smaller down payment
Change one input — put 10% down instead of 20% — and three things move at once. The loan grows to $405,000, so principal and interest rises to $2,626.82. PMI switches on at 0.6% of the loan, adding $202.50 a month. The total payment becomes $3,541.82, which is $494 more every month than the 20%-down version. Over the full term, the larger loan also accrues about $540,656 of interest instead of $480,583. None of this means a smaller down payment is wrong — waiting years to save 20% has its own cost — but the trade-off should be a number, not a vibe.
Where the money goes: interest first, equity later
Amortization front-loads interest. In month one of the $360,000 loan, $2,025.00 of the $2,334.95 payment is interest and only $309.95 reduces the balance. Over 30 years you repay the $360,000 you borrowed plus $480,583 in interest — the house costs roughly 2.3× the loan amount. The first-month split shown in the results panel is there precisely because it surprises most first-time buyers.
Three levers change that interest bill dramatically:
- Term. The same loan over 15 years costs $3,185.67 a month but only $213,421 in lifetime interest — a saving of about $267,000 versus the 30-year schedule.
- Rate. At 6.0% the payment is $2,158.38; at 7.5% it is $2,517.17. A percentage point and a half moves the payment by about $360 a month, which is why shopping multiple lenders and considering points can matter more than negotiating the sale price.
- Extra principal. Adding just $200 a month to the default loan pays it off in about 23.8 years instead of 30 and cuts lifetime interest by roughly $115,900. Extra payments early in the loan do the most work, because that is when the balance — and therefore the interest — is largest.
What this estimate deliberately leaves out
A payment estimate is not a closing estimate. One-time costs — origination fees, title insurance, appraisal, transfer taxes, prepaid escrow — typically add 2–5% of the purchase price at closing and are not part of the monthly figure here. The calculator also treats property tax and insurance as fixed, while in reality both tend to rise over the years; models a fixed rate, so adjustable-rate mortgages behave differently after their intro period; and does not predict when PMI cancels. Use the monthly number for affordability decisions, then get a formal Loan Estimate from a lender for the transaction itself.
Frequently asked questions
Why is most of my early mortgage payment interest?
Interest is charged on the outstanding balance, and the balance is at its largest in month one. On a $360,000 loan at 6.75%, the first $2,334.95 payment splits into $2,025.00 interest and only $309.95 principal. Each month the balance falls slightly, so the interest share shrinks and the principal share grows — slowly at first, then faster in the final decade.
How do I avoid paying PMI?
Conventional lenders typically require private mortgage insurance when your down payment is below 20% of the purchase price. Putting 20% down avoids it entirely. If you buy with less down, PMI can usually be cancelled once you reach 20% equity through payments or appreciation — this calculator shows the PMI cost but does not model the cancellation date.
What is the 28% housing ratio guideline?
A common lender rule of thumb says your total monthly housing payment should stay at or below 28% of gross monthly income. It is a screening guideline, not a law — lenders also weigh your other debts, credit history, and reserves. The calculator shows your ratio so you can see how a specific price and rate compare to that benchmark.
Will my monthly payment stay the same for 30 years?
On a fixed-rate loan the principal-and-interest portion never changes. The rest of the payment can: property taxes are reassessed, insurance premiums rise, and HOA dues increase. That is why a payment quoted as "fixed" still drifts upward over the years if you escrow taxes and insurance.
What is the difference between interest rate and APR?
The interest rate is what the amortization math uses to compute your payment. APR bundles the rate with certain lender fees and points to give a standardized cost-comparison number, so APR is normally a little higher than the rate. When comparing two loan offers with different fees, APR is the fairer yardstick; when estimating your payment, use the note rate.
Is a 15-year mortgage worth the higher payment?
On a $360,000 loan at 6.75%, the 15-year payment is $3,185.67 versus $2,334.95 for 30 years — about $850 more each month. In exchange, lifetime interest falls from $480,583 to $213,421, a saving of roughly $267,000. Whether that trade is worth it depends on whether the higher payment crowds out retirement savings or an emergency fund.