Frequently Asked Questions
How is the monthly mortgage payment calculated?
The principal-and-interest payment 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 (the annual rate divided by 12) and n is the number of monthly payments (the term in years times 12). The result is the fixed payment that pays the loan off exactly over the term, with the same amount due every month. If you add annual property tax and home insurance, the calculator divides each by 12 and adds them on top to show a fuller monthly housing cost, often called PITI. When the interest rate is zero, the formula breaks down mathematically, so the calculator falls back to simply dividing the loan amount by the number of months. Because everything is computed in your browser, you can change any input and watch the payment update instantly without sending your numbers anywhere.
What is an amortization schedule?
An amortization schedule shows how each payment splits between interest and principal over the life of the loan. Early on, most of the payment goes to interest because the outstanding balance is large; over time the balance shrinks and a growing share of each payment goes to principal, which is how you build equity. This calculator condenses the month-by-month math into a year-by-year table showing interest paid, principal paid and the remaining balance at the end of each year, so you can see the crossover point where principal starts to dominate. The total interest figure shown above the schedule is simply the sum of every monthly interest portion across the whole term. Reading the schedule makes it clear why paying even a little extra principal early saves a disproportionate amount of interest later.
Does it include taxes and insurance?
Optionally, yes. The property tax and home insurance fields are annual amounts, and you can leave them at zero to see just principal and interest. When you enter them, the calculator adds one-twelfth of each to the monthly payment so you get a closer estimate of your true monthly outlay, the figure lenders call PITI (principal, interest, taxes and insurance). It does not include private mortgage insurance (PMI), homeowners-association (HOA) dues, utilities, maintenance, or escrow shortfalls, and real tax and insurance amounts drift over time as assessments and premiums change. For that reason, treat the combined figure as a planning estimate rather than an exact bill. If you want to compare the pure cost of borrowing across different rates or terms, set both fields to zero and read the principal-and-interest line on its own.
Is this mortgage estimate accurate enough to rely on?
It is accurate for the math it actually performs — the payment, total interest and amortization schedule are computed with the exact amortization formula at full floating-point precision, then rounded only for display. What it cannot know is everything that makes a real quote unique to you: your credit score, down payment, loan type, discount points, lender fees, closing costs, and the rounding each lender applies. None of those are modeled here. The right way to use the tool is to compare scenarios side by side — see how a lower rate or a shorter term changes the payment and the lifetime interest — and then confirm the final, binding numbers with a lender before you commit. Everything runs entirely in your browser, so the loan amount, rate and other figures you type stay private and are never uploaded to a server.
How do the interest rate and term change the payment and total interest?
Rate and term pull the two headline numbers — the monthly payment and the total interest — in opposite directions, so it helps to test them separately. A higher interest rate raises both the monthly payment and the total interest, because every month's interest is charged on the outstanding balance; even half a percentage point can add a noticeable amount over a 30-year loan. The term works differently: a longer term spreads the principal over more payments, which lowers the monthly amount but increases total interest, since the balance is carried — and charged interest on — for more years. A shorter term does the reverse, with a higher monthly payment but far less interest overall. Because this calculator recomputes instantly, the fastest way to understand the trade-off is to nudge the rate or term up and down and watch the monthly payment and total-interest figures move together.
Should I choose a 15-year or 30-year mortgage?
The choice comes down to a trade-off between monthly affordability and lifetime cost, and this calculator lets you see both sides by simply changing the term from 30 to 15. A 30-year term keeps the monthly payment lower because the principal is spread across 360 payments, which is easier on a monthly budget but means you pay interest for far longer, so total interest is high. A 15-year term roughly compresses the same principal into 180 payments, so the monthly payment is meaningfully higher, but the loan is paid off in half the time and the total interest is dramatically lower. Enter your loan amount and rate, calculate at 30 years, then switch the term to 15 and compare the monthly payment and total-interest lines. The right answer depends on whether the higher 15-year payment still fits comfortably alongside your other expenses.