Mortgage Calculator

Calculate Your Monthly Mortgage Payment Before You Fall in Love With a House

There's a pattern that catches first-time homebuyers off guard more consistently than almost anything else in the purchase process: finding a house that feels right, becoming emotionally invested in owning it, and only then doing the math to see whether the monthly payment is actually sustainable within your budget. By that point, the decision has already been shaped by emotion rather than arithmetic. Our free mortgage calculator reverses that sequence—letting you calculate the monthly principal and interest payment for any home price and interest rate combination in under five seconds, before you ever step through a front door.

Enter the home price (or loan amount if you've already determined your down payment), the annual interest rate, and the loan term in years. The calculator returns the monthly payment on principal and interest, plus the total amount paid over the full life of the loan—a figure that often reframes the conversation about what a 30-year commitment actually costs in total interest terms. Use it early and often: to establish an affordability ceiling before starting your search, to compare payment scenarios across different price points, to evaluate how rate changes shift your payment, and to model the monthly cost difference between 15-year and 30-year loan terms.

How Your Monthly Mortgage Payment Is Calculated

A standard fixed-rate mortgage is an amortizing loan—each monthly payment covers the interest that has accrued on the outstanding balance plus a portion of the principal, until the final payment pays off the balance completely. The payment amount is fixed throughout the loan term, but the internal allocation between interest and principal shifts with every payment. Early payments are heavily weighted toward interest; later payments go predominantly to principal.

The monthly payment formula is: M = P × [r(1+r)^n] ÷ [(1+r)^n − 1], where P is the loan principal, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments (years × 12). This formula produces the exact payment amount that zeros out the balance after the last scheduled payment. Our calculator applies this formula with full precision.

15-Year vs. 30-Year Mortgage: What the Numbers Show

The choice between a 15-year and 30-year term is one of the most financially significant decisions in the homebuying process. Running both scenarios through our calculator immediately quantifies the trade-off between monthly affordability and total interest cost—a comparison that's easy to understand conceptually but often more dramatic in dollar terms than people expect.

On a $300,000 mortgage at 6.5% interest: the 30-year monthly payment is approximately $1,896, and total payments over the life of the loan reach roughly $682,560—meaning approximately $382,560 goes to interest, more than the original $300,000 borrowed. The 15-year monthly payment jumps to approximately $2,614—a $718 increase per month—but total payments fall to roughly $470,520, saving over $212,000 in interest compared to the 30-year option.

The 15-year loan also builds equity nearly twice as fast during the early years of ownership, which matters if you plan to refinance, sell, or borrow against the equity within a relatively short window. That said, the $718 per month difference is genuinely significant for most household budgets. If the higher payment would leave your cash flow uncomfortably tight, or prevent you from maintaining an emergency fund and investing in tax-advantaged retirement accounts, the 30-year loan's flexibility may be worth the additional interest cost over the full term.

How Interest Rate Changes Affect Affordability

Mortgage interest rates exert an unusually large influence on monthly affordability because home loan amounts are large and terms are long. Even a half-percentage-point rate difference produces a meaningful payment change that compounds across decades of monthly payments.

On a $350,000 loan over 30 years: at 5.5%, the monthly payment is approximately $1,987. At 6.5%, it rises to $2,212—a $225 monthly increase and roughly $81,000 in additional total interest. At 7.5%, the payment reaches $2,448—$461 more per month than at 5.5%, and approximately $165,000 more in total interest. These differences explain why prospective buyers in rising-rate environments often reduce their purchase price targets rather than absorbing the full payment impact of higher rates on their original budget.

Our calculator is particularly useful for modeling rate sensitivity. If you're shopping in a volatile rate environment—or locking a rate while rates are fluctuating—running the calculation at the current rate, at a rate 0.5% higher, and at a rate 0.5% lower gives you a clear sense of your payment range and helps you set a purchase price ceiling that remains comfortable across the plausible range of closing rates.

What the Calculator Doesn't Include: Planning for Total Housing Cost

The monthly payment our calculator produces covers principal and interest only. Understanding your full monthly housing cost requires adding several additional expense categories that every homeowner faces but that vary significantly by property type, location, and loan structure.

Property taxes are assessed annually based on the assessed value of your property and local tax rates. They vary enormously by state and municipality—from below 0.5% annually in some Southern states to above 2% in parts of the Northeast. Divide your expected annual property tax bill by 12 and add that to your monthly housing budget. Homeowners insurance is required by virtually all mortgage lenders and typically runs $1,000 to $2,500 annually depending on home value, location, coverage level, and claims history. For loans with less than 20% down payment, Private Mortgage Insurance (PMI) adds roughly 0.5% to 1.5% of the original loan amount per year until you reach 20% equity, which can add $100 to $300 per month to your effective cost.

Additionally, ongoing maintenance and repairs—which most financial advisors budget at 1% to 2% of home value annually—represent a genuine cost of ownership that renters don't face. A $350,000 home may need $3,500 to $7,000 in maintenance work in an average year. This isn't a monthly line item that you pay every month, but it's a cash flow requirement that your budget needs to accommodate. When all these costs are added to principal and interest, the true monthly cost of homeownership typically runs 30% to 50% higher than the mortgage payment alone.

How Much House Can I Actually Afford?

Lenders typically qualify borrowers using a debt-to-income (DTI) ratio, which compares total monthly debt payments to gross monthly income. The conventional guideline suggests that housing costs (principal, interest, taxes, and insurance) should not exceed 28% of gross monthly income, and total monthly debt payments should not exceed 36% to 43% of gross income. However, lender qualification criteria represent the maximum you can borrow—not necessarily the payment level that will feel comfortable to your actual lifestyle and financial priorities.

A more conservative personal budgeting approach targets housing costs at 25% or less of take-home (after-tax) income rather than gross income. Working backward from that threshold: if your take-home pay is $6,000 per month, a 25% target suggests a total monthly housing cost of $1,500 or below. Subtract your estimated taxes, insurance, and PMI to find the principal-and-interest payment that fits that target, then work backward through our calculator to find the loan amount that produces that payment at current rates.

Completely Free, Completely Private

The mortgage calculator runs entirely within your browser. No home prices, interest rates, or financial details you enter are transmitted to any server or stored anywhere outside your current session. The tool is completely free with no account or registration required. Model as many purchase scenarios as your homebuying process demands—different price points, rate assumptions, and loan terms—with complete confidence that your financial information stays on your device.