Mortgage Calculator — Monthly Payment, PITI & Amortization

What this mortgage calculator actually estimates

Type in a home price, a down payment, an interest rate and a term, and this mortgage calculator returns your estimated monthly payment — not just the bare principal and interest, but the full PITI figure that budgets and lenders actually run on: Principal, Interest, Taxes and Insurance, with PMI and HOA folded in when they apply. Every number is computed in your browser as you type, so nothing you enter is uploaded, stored, or shared — you can model a real offer without handing your finances to a server.

You can switch the currency between USD, GBP, EUR, CAD and AUD, flip between a 15-, 20- or 30-year term, and add an extra monthly payment to watch the interest saved and the payoff date update live. First-time buyers can size up what a given home price really costs each month before they ever talk to a lender; if you already own, you can compare a new rate and term against your current loan to check whether refinancing pays off. It pairs well with an EMI calculator for non-US loan formats or a debt payoff plan for what the mortgage leaves behind. Treat every figure here as a planning estimate — it is not a loan offer, a pre-approval, or financial advice.

A worked PITI breakdown on a $400,000 home

Say the home is $400,000 and you put 10% down — that’s a $40,000 down payment and a $360,000 loan, a 90% loan-to-value. At a 6.39% APR over 30 years, with property tax of $4,800/yr and home insurance of $1,800/yr, here is how the monthly payment splits apart. Because the down payment is under 20% (LTV above 80%), the calculator also adds an estimated PMI line, and it rounds each figure to the nearest whole dollar so the parts sum cleanly to the total:

Over the full 30 years, the principal-and-interest alone costs about $449,807 in total interest — more than the house. That’s exactly where extra payments earn their keep: on this loan, an extra $200 a month cuts roughly $105,939 of interest and pays the mortgage off about 6 years early. The amortization schedule under the calculator shows the same story year by year, as each payment shifts from mostly interest toward mostly principal.

The math behind the monthly payment

The principal-and-interest portion uses the standard fixed-rate amortization formula. Only three inputs drive it — the loan amount, the monthly rate, and the number of payments:

r = APR / 12 / 100          (monthly interest rate)
                n = years * 12              (total number of payments)

                        P * r * (1 + r)^n
                M  =  ---------------------
                         (1 + r)^n  -  1

Here P is the loan amount (home price minus down payment), r is the monthly rate, and n is the number of months. If you set the rate to zero, it falls back to a simple P / n. Every month the calculator charges interest on the remaining balance and puts the rest toward principal — that month-by-month walk is what produces the amortization schedule, the total interest, and the payoff date. Property tax, home insurance, PMI and HOA are added on top of this to give the full PITI number; they don’t change the underlying loan math.

Two honest limits. First, this is a fixed-rate model: it assumes your rate never changes, so an adjustable-rate mortgage (ARM) that resets later will diverge from these figures. Second, and more important, it’s an estimate, not a loan offer. It doesn’t include closing costs, lender fees, discount points, or escrow adjustments, and your tax, insurance and PMI figures are estimates or your own inputs. Rates also vary by credit score, term and region. For a binding number, get a written Loan Estimate from a lender — nothing here is financial advice.

15, 20 or 30 years: what the term does to total interest

Shortening the term raises the monthly payment but slashes the total interest, because you repay the principal faster and pay less of it to the bank. Here is the same $360,000 loan at 6.39%, changing only the term:

The 15-year here costs about $864 more a month than the 30-year but saves roughly $249,000 in interest. And this table holds the rate constant to isolate the term — in the real market lenders usually price 15-year loans a little lower, so the gap is often wider still. At a typical 5.70% the 15-year’s total interest drops to around $176,372. Toggle the term buttons above the calculator to compare 15, 20 and 30 years against your own numbers.

When you pay PMI — and when it comes off

Private Mortgage Insurance (PMI) protects the lender, not you, and it’s generally required when your down payment is below 20% — that is, when your loan-to-value is above 80%. This calculator watches that threshold: drop the down-payment slider under 20% and it automatically adds an estimated PMI line at about 0.5% of the loan per year. On the $360,000 loan above that’s roughly $150 a month, and the calculator flags it right on the down-payment slider.

In the United States, borrower-paid PMI on a conforming loan doesn’t last forever. Under the federal Homeowners Protection Act it must automatically terminate once the balance reaches 78% of the original home value, and you can request cancellation earlier at 80% LTV — reached either by paying down the balance or, with a fresh appraisal, by the home appreciating. One caveat to read the tool honestly: it shows PMI as a flat monthly estimate and does not model the exact month it stops, so treat that line as a planning figure. Rules differ abroad, too — insurance for a low deposit goes by other names and follows different terms outside the US (for example, Lenders Mortgage Insurance in Australia), so confirm what applies in your market.

Common pitfalls, and when not to lean on the estimate

Reading principal and interest as your whole payment

A P&I-only figure can understate your real cost by hundreds a month. Open the “taxes, insurance & HOA” panel so the result reflects the full PITI you’ll actually budget for.

Treating today’s rate as locked

Mortgage rates move weekly, and an adjustable-rate loan can reset years in. The Latest Mortgage Rate News panel is a reference for direction, not a quote — always confirm the current rate with a lender before you rely on a payment.

Guessing property tax and insurance

These swing enormously by county, state and property, and they’re your inputs here, not a lookup. Plug in the actual figures from a listing or an insurance quote rather than leaving the defaults.

Forgetting the costs it doesn’t model

Closing costs, lender fees, discount points and escrow shortfalls aren’t in the monthly figure. For the binding breakdown, compare lenders’ official Loan Estimates — this tool is for planning, not underwriting.

Used within those limits, the calculator is a fast way to pressure-test a home price, a down payment, a 15- vs 30-year term, and extra payments before you talk to anyone — whether you’re a first-time buyer running the numbers on a first offer or an owner checking whether a refinance pays off. Just remember every output is an estimate for planning — not a loan offer, and not financial advice.

Frequently asked questions