Mortgage Calculator

How to Use This Mortgage Calculator

Enter the home price, your down payment amount, the annual interest rate from your lender, and choose your preferred loan term. The calculator instantly shows your estimated monthly payment broken down into principal, interest, property taxes, insurance, and PMI if applicable. The total monthly payment gives you the complete picture of what you'll actually pay each month, not just the loan portion.

Understanding Your Monthly Payment (PITI)

Your mortgage payment consists of four parts, commonly known as PITI. Principal is the portion that reduces your loan balance — early in the loan, this is a small fraction of your payment, growing larger over time. Interest is what the lender charges for borrowing the money. Property taxes are collected monthly by your lender and held in an escrow account to pay your annual tax bill. Insurance includes homeowner's insurance and, if your down payment is less than 20%, Private Mortgage Insurance (PMI) that protects the lender in case you default.

Added together, that's exactly the formula shown above your results:

$$\text{Total} = \text{P\&I} + \frac{\text{Tax}}{12} + \frac{\text{Insurance}}{12} + \text{PMI}$$

How the Amortization Formula Works

Your monthly principal-and-interest payment stays fixed for the life of the loan. It's calculated with the standard fixed-rate mortgage amortization formula:

$$M = P \cdot \frac{r(1+r)^n}{(1+r)^n - 1}$$

In the early years of a 30-year mortgage, roughly 70-80% of each payment goes toward interest rather than principal — that ratio gradually flips, so most of each payment reduces the principal by the final years. That's why the "Cumulative Loan Balance Over Time" chart above curves instead of declining in a straight line.

Worked Example: 300,000-Dollar Home with 20% Down

Using the calculator's own default numbers above — a 300,000-dollar home price, a 60,000-dollar down payment (20%, so no PMI applies), a 6.5% annual interest rate, and a 30-year term — here's how the formula plays out.

First, find the loan principal: $P = \$300{,}000 - \$60{,}000 = \$240{,}000$. Next, convert the annual rate to a monthly rate: $r = 6.5\% / 12 \approx 0.005417$. The number of payments is $n = 30 \times 12 = 360$.

Plugging these into the formula above gives a monthly principal-and-interest payment of about 1,517 dollars — the calculator above shows this exact figure, plus the property tax, insurance, and total-interest breakdown, since it loads with these same default values. Over the full 30-year term, that adds up to roughly 306,000 dollars in total interest — more than the original loan amount, which is why comparing loan terms matters as much as comparing rates (see the FAQ below).

Worked Example: 15-Year vs. 30-Year on the Same Loan

Take the same 240,000-dollar loan principal from the example above at the same 6.5% rate, and compare only the term length. Over 30 years, the payment works out to about 1,517 dollars a month, as shown above, with roughly 306,000 dollars paid in interest by the end. Run that identical loan over 15 years instead, and the monthly payment rises to about 2,091 dollars — 574 dollars more each month — but total interest drops to about 136,318 dollars, a savings of roughly 169,788 dollars over the life of the loan.

That comparison uses the same rate for both terms to isolate the effect of the term length alone. In practice, lenders typically price 15-year loans somewhat lower than 30-year loans on the same day — often by a quarter to half a percentage point — since a shorter loan is less risky for the lender, which would make the 15-year option even more favorable than the numbers above suggest. The tradeoff is entirely about monthly cash flow: a 30-year term is the only way most buyers can qualify for a given home price at all, while a 15-year term suits buyers who can comfortably absorb the higher payment and want to be debt-free sooner.

Tips for Getting a Better Mortgage Rate

A higher credit score (740 or above) typically qualifies you for the lowest available rates. Making a larger down payment, ideally 20% or more, eliminates the need for PMI and may secure better terms from lenders. Shopping at least three to five lenders before committing can save thousands over the life of the loan. Consider the total cost of the loan rather than focusing solely on the monthly payment — a 15-year mortgage has higher monthly payments but saves tens of thousands in total interest compared to a 30-year term.

Fixed-Rate vs. Adjustable-Rate Mortgages

This calculator models a fixed-rate mortgage, where the interest rate — and therefore the principal-and-interest payment — never changes for the entire loan term. The alternative is an adjustable-rate mortgage (ARM), which holds a lower introductory rate fixed for an initial period, commonly 5, 7, or 10 years, then adjusts periodically after that based on a market index plus a lender margin. A "5/1 ARM" is fixed for 5 years, then adjusts once a year afterward.

ARMs typically start with a noticeably lower rate than a comparable fixed loan, which appeals to buyers who expect to sell or refinance before the adjustable period begins, or who simply want the lowest possible payment today and are willing to accept uncertainty later. The risk is exactly that uncertainty: if market rates have risen by the time your ARM adjusts, your payment can jump substantially with little warning, whereas a fixed-rate borrower's payment is completely insulated from that risk for the full term. Most first-time buyers who plan to stay in a home long-term are better served by the predictability of a fixed rate, even at a somewhat higher starting number.

When (and Whether) to Refinance

Refinancing replaces your existing mortgage with a new one — usually to secure a lower interest rate, shorten or extend the term, switch from an adjustable to a fixed rate, or convert home equity into cash (a "cash-out" refinance). It isn't free: expect closing costs similar in scope to the original purchase, typically 2% to 5% of the loan amount, covering appraisal, origination, title work, and other lender fees.

The standard way to judge whether refinancing is worth it is the break-even point: divide the closing costs by your monthly savings to find how many months it takes the savings to cover the cost of refinancing itself. Six thousand dollars in closing costs against 200 dollars in monthly savings breaks even in 30 months, for example. If you plan to stay in the home well past that point, refinancing usually makes sense; if you might move or sell before then, it often doesn't. Refinancing also restarts your amortization schedule from year one, so refinancing late into an existing loan can mean paying more total interest even at a lower rate — running the new terms through a calculator like this one before committing is worth the two minutes it takes.

A Brief History of the Mortgage

Mortgages are much older than the 30-year fixed product most buyers use today. The word itself comes from Old French: mort ("dead") plus gage ("pledge") — a "dead pledge," because the obligation ends either when the debt is fully repaid and the pledge on the property dies, or when the borrower defaults and forfeits it. Despite the grim etymology, home lending in anything resembling its current form is largely a 20th-century invention.

Before the 1930s, US mortgages typically ran just 5 to 10 years, were often interest-only, and ended in a large balloon payment — borrowers usually rolled that balloon into a fresh short-term loan rather than paying it off outright, which depended on banks having the credit available to keep extending new loans. When the Great Depression froze credit and home values collapsed, huge numbers of borrowers who had been paying reliably for years suddenly couldn't refinance their balloon payments, and lost their homes anyway.

In response, the National Housing Act of 1934 created the Federal Housing Administration (FHA), which insured lenders against default on long-term, fully amortizing loans — the structure this calculator is built around, where every payment is level and the loan pays itself off completely by the end of the term. In 1938 the government chartered the Federal National Mortgage Association (Fannie Mae) to buy FHA-insured loans from banks, freeing up their capital to issue more of them; that's the origin of the "secondary market" that still underpins most US mortgage lending today (Freddie Mac followed in 1970 as a second buyer, adding competition). Combined with the VA loan program after World War II, these changes turned the long-term fixed-rate mortgage from a rarity into the default way most Americans buy a home. Rates have swung dramatically since: they peaked above 18% in the early 1980s as the Federal Reserve fought runaway inflation, and touched historic lows near 3% in 2020-2021 — a reminder that the rate environment at any given moment is a snapshot, not a constant.

Common Mortgage Mistakes to Avoid

Comparing lenders by interest rate alone while ignoring fees and points is a common trap — a lower rate paired with high origination fees can cost more overall than a slightly higher no-point rate, which is exactly why APR (covered below) is a fairer number to shop with than the bare interest rate. Borrowing right up to the maximum a lender pre-approves is another: that figure reflects the most a lender is willing to risk, not necessarily the most you can comfortably afford once property taxes rise, an HOA fee appears, or income dips. Skipping a home inspection to make an offer more competitive can hide expensive repairs that a routine appraisal won't catch on its own. And treating the monthly payment as the only number that matters overlooks the total interest paid over the full term — visible directly in the amortization schedule above — which is often the largest single cost of the entire transaction.

Mortgage Terms You Should Know

Escrow Account — An account your lender uses to collect a portion of your property taxes and insurance with every monthly payment, then pays those bills on your behalf when they're due, so you never have to save separately for one large annual bill.

Home Equity — The portion of your home you actually own outright: current market value minus your remaining loan balance. Equity grows both as you pay down principal and as the home's value appreciates.

Loan-to-Value Ratio (LTV) — Your loan amount divided by the home's appraised value, expressed as a percentage. A 240,000-dollar loan on a 300,000-dollar home is an 80% LTV — exactly the threshold where PMI typically drops off.

Debt-to-Income Ratio (DTI) — Your total monthly debt payments, including the new mortgage, divided by your gross monthly income. Lenders use DTI alongside credit score to decide how much they're willing to lend.

APR vs. Interest Rate — The interest rate applies only to your loan balance. Annual Percentage Rate (APR) folds in most lender fees and points too, spread over the loan term, which is why APR is almost always slightly higher than the quoted rate and is the fairer number for comparing offers between lenders.

Discount Points — An upfront fee paid at closing to buy down your interest rate for the life of the loan. One point typically costs 1% of the loan amount and lowers the rate by roughly a quarter of a percentage point, though the exact tradeoff varies by lender.

Closing Costs — The fees due at signing beyond the down payment itself — appraisal, title insurance, origination fees, and more — typically 2% to 5% of the loan amount.

Prepayment Penalty — A fee some loans charge if you pay off the balance early, whether through refinancing or extra payments. Most conventional US mortgages today don't carry one, but it's worth confirming before making large extra payments.

This calculator provides estimates for educational and planning purposes only. Actual mortgage payments may vary based on lender requirements, exact interest rates, local tax rates, insurance premiums, and other factors. Consult a qualified financial advisor or mortgage professional for guidance specific to your situation.