Mortgage Calculator
Calculate monthly mortgage payments, total interest, and total payment amount. Enter principal, interest rate, and loan term.
Key features
- Monthly payment calculation
- Total interest display
- Amortization summary
- Various term lengths
Guide
A mortgage is a loan used to purchase real estate, where the property itself serves as collateral. Monthly mortgage payments are the largest recurring expense for most homeowners. Understanding how mortgage payments are calculated helps you make informed decisions about how much house you can afford, which loan terms to choose, and whether refinancing makes financial sense. This guide covers the math behind mortgage calculations, the factors that affect your payment, and strategies for managing mortgage costs. The standard mortgage payment formula calculates a fixed monthly payment that, over the life of the loan, pays off both the principal (the amount borrowed) and the interest (the lender's charge for lending you the money). The formula is: M = P times [r times (1 + r)^n] divided by [(1 + r)^n minus 1], where M is the monthly payment, P is the principal loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of payments (loan term in years times 12). A concrete example makes this clearer. For a $300,000 loan at 6.5% annual interest for 30 years: the monthly rate r is 0.065 divided by 12, which equals 0.005417. The number of payments n is 30 times 12, which equals 360. Plugging into the formula gives a monthly payment of approximately $1,896.20. Over 30 years, you will pay a total of $682,632, meaning you pay $382,632 in interest on top of the $300,000 principal. Interest nearly doubles the cost of the home. The interest rate is the single biggest factor affecting your monthly payment and total cost. On a $300,000 30-year loan, the difference between 6% and 7% interest changes the monthly payment from $1,799 to $1,996, a difference of $197 per month. Over 30 years, that 1% rate difference costs an additional $70,920. Shopping for the best rate and improving your credit score before applying can save tens of thousands of dollars. Getting quotes from at least three lenders is standard advice because rates and fees vary significantly between institutions. Loan term length creates a trade-off between lower monthly payments and lower total interest paid. A 30-year mortgage on $300,000 at 6.5% costs $1,896 per month and $382,632 in total interest. A 15-year mortgage on the same loan costs $2,613 per month but only $170,388 in total interest. The 15-year loan has monthly payments that are $717 higher, but it saves $212,244 in interest and builds equity twice as fast. A 20-year term offers a middle ground with payments of approximately $2,239 and total interest of approximately $237,360. Amortization describes how each monthly payment is split between principal and interest over time. In the early years of a 30-year mortgage, most of your payment goes to interest. On a $300,000 loan at 6.5%, the first payment of $1,896.20 consists of $1,625.00 in interest and only $271.20 in principal. By month 180 (halfway through the loan), the split is approximately $1,119 in interest and $777 in principal. By the final year, nearly the entire payment goes to principal. This front-loaded interest structure is why paying extra toward principal in the early years has such a large impact on total interest paid. An amortization schedule is a table showing every payment over the life of the loan with the principal portion, interest portion, and remaining balance. Reviewing this schedule reveals how slowly equity builds in the early years. After five years of payments on a 30-year $300,000 loan at 6.5% (60 payments totaling $113,772), you have paid approximately $95,665 in interest and only $18,107 in principal. Your remaining balance is still $281,893. This reality check motivates many homeowners to make extra principal payments early in the loan. Down payment size directly affects the loan amount and therefore the monthly payment. A 20% down payment on a $375,000 home means you borrow $300,000. A 10% down payment means you borrow $337,500, increasing the monthly payment by about $237 on a 30-year loan at 6.5%. A 5% down payment means borrowing $356,250 and even higher payments. Beyond the payment difference, down payments below 20% typically require private mortgage insurance (PMI), which adds $50 to $200 or more per month depending on the loan amount and your credit profile. PMI protects the lender if you default and provides no benefit to you. It is removed once you reach 20% equity, either through payments or home value appreciation. Property taxes and homeowners insurance are not part of the mortgage calculation itself but are often bundled into your monthly payment through an escrow account. The lender collects these amounts monthly and pays the tax authority and insurance company on your behalf. Your total housing payment (often called PITI: Principal, Interest, Taxes, and Insurance) is significantly higher than the principal and interest alone. Property taxes average 1.1% of home value nationally but range from 0.3% in Hawaii to 2.5% in New Jersey. Homeowners insurance averages $1,500 to $3,000 per year for a typical home. On a $375,000 home, property taxes and insurance could add $400 to $750 per month to your PITI payment. Fixed-rate mortgages lock in your interest rate for the entire loan term. Your principal and interest payment never changes regardless of market conditions. This predictability makes budgeting straightforward. Adjustable-rate mortgages (ARMs) start with a lower interest rate for an initial period (typically 5, 7, or 10 years), then adjust periodically based on a market index. A 5/1 ARM has a fixed rate for 5 years, then adjusts every year. ARMs carry the risk that your payment could increase substantially after the initial fixed period, but they offer lower initial payments and can save money if you plan to sell or refinance before the adjustment period. ARM rate caps limit how much the rate can increase per adjustment period (typically 2%) and over the life of the loan (typically 5 to 6% above the initial rate). Extra payments toward principal accelerate your payoff and reduce total interest. Adding $200 per month to the principal payment on a $300,000 30-year loan at 6.5% shortens the loan term by about 6 years and saves approximately $100,000 in interest. Even one extra payment per year (equivalent to paying biweekly instead of monthly, resulting in 13 annual payments instead of 12) significantly reduces the total interest and loan duration. Most lenders allow extra principal payments without penalty, but verify your loan has no prepayment penalty before committing to this strategy. Refinancing replaces your existing mortgage with a new one, typically to get a lower interest rate, change the loan term, or switch from an ARM to a fixed rate. The general rule is that refinancing makes sense when you can reduce your rate by at least 0.5 to 1 percentage point and plan to stay in the home long enough to recoup closing costs (typically 2 to 5% of the loan amount). Calculate the break-even point: divide the total closing costs by the monthly savings to determine how many months until the refinance pays for itself. If closing costs are $6,000 and you save $200 per month, the break-even point is 30 months. Cash-out refinancing lets you borrow more than your current mortgage balance, taking the difference as cash. This uses your home equity to fund renovations, debt consolidation, or other expenses. The downside is a larger loan balance and potentially higher interest rate. Home equity lines of credit (HELOCs) offer an alternative way to tap equity without refinancing the entire mortgage. Debt-to-income ratio (DTI) is a key factor lenders use to determine how much you can borrow. Your DTI is total monthly debt payments (mortgage, car loans, student loans, credit card minimums) divided by gross monthly income. Most conventional lenders require a DTI below 43%, with some allowing up to 50% for strong applications. FHA loans allow up to 57% in some cases. A lower DTI means you qualify for better rates and larger loan amounts. Reducing other debts before applying for a mortgage improves your borrowing capacity. Credit score affects the interest rate you qualify for. Borrowers with scores above 760 get the best rates. Scores between 700 and 759 get slightly higher rates. Scores between 620 and 699 get noticeably higher rates and may face stricter terms. Below 620, conventional loans become difficult to obtain, though FHA loans are available with scores as low as 580 (with 3.5% down) or 500 (with 10% down). Improving your credit score by paying down credit card balances, fixing errors on your credit report, and avoiding new credit applications in the months before applying for a mortgage can save significant money over the life of the loan. Loan types have different requirements and costs. Conventional loans require higher credit scores but offer competitive rates and no upfront mortgage insurance fees. FHA loans accept lower scores and smaller down payments but charge an upfront mortgage insurance premium (1.75% of the loan) plus monthly insurance that lasts the entire loan term for loans with less than 10% down. VA loans (for military veterans) require no down payment and no PMI but charge a funding fee. USDA loans serve rural areas with no down payment for qualifying properties and incomes. Closing costs are fees paid at the time of purchase or refinance. They typically range from 2% to 5% of the loan amount and include origination fees, appraisal fees, title insurance, attorney fees, recording fees, and prepaid items like property taxes and insurance. On a $300,000 loan, closing costs might range from $6,000 to $15,000. Some lenders offer no-closing-cost mortgages, but they compensate by charging a higher interest rate, which costs more over the long term. Comparing mortgage offers requires looking beyond the interest rate. The Annual Percentage Rate (APR) includes the interest rate plus certain fees, giving a more complete picture of the loan cost. A loan at 6.5% with $5,000 in fees has a higher APR than a loan at 6.5% with $2,000 in fees. Compare APR, not just the quoted interest rate, when evaluating lenders. Also compare loan estimates (standardized disclosure documents) from at least three lenders before choosing. House affordability depends on more than the mortgage payment. Budget for maintenance (plan for 1% to 2% of the home's value annually), utilities (which may be higher than your current costs), HOA fees if applicable, and the opportunity cost of the down payment (that money is no longer available for other investments). A common guideline is that total housing costs should not exceed 28% of gross monthly income, with total debt payments (including housing) not exceeding 36%. Mortgage points (discount points) let you buy a lower interest rate upfront. One point costs 1% of the loan amount and typically reduces the rate by 0.25%. On a $300,000 loan, one point costs $3,000 and might reduce the rate from 6.5% to 6.25%, saving about $60 per month. The break-even point is $3,000 divided by $60, which equals 50 months (about 4 years). If you plan to stay in the home longer than 4 years, buying points saves money. If you plan to move sooner, skip the points. Mortgage interest deduction is a tax benefit for homeowners who itemize deductions. You can deduct interest on up to $750,000 of mortgage debt ($375,000 if married filing separately) for loans originated after December 15, 2017. For a $300,000 loan at 6.5%, first-year interest is about $19,400, which exceeds the standard deduction for single filers ($14,600 in 2024). Whether the mortgage interest deduction benefits you depends on whether your total itemized deductions exceed the standard deduction. State and local tax deductions (SALT), capped at $10,000, are often combined with mortgage interest to surpass the standard deduction threshold. Interest rate locks protect you from rate increases between application and closing. A rate lock guarantees your quoted rate for a set period, typically 30 to 60 days. If rates rise during that period, your locked rate holds. If rates drop significantly, some lenders offer float-down provisions that let you take the lower rate. Rate locks matter because closing often takes 30 to 45 days, and rates can move significantly in that time. A rate increase of 0.25% on a $300,000 loan adds about $50 per month and $18,000 over the loan term. Home equity builds as you pay down the mortgage and as the home appreciates in value. Equity equals the home's current market value minus the remaining mortgage balance. If your home is worth $400,000 and you owe $280,000, you have $120,000 in equity. Building equity is a form of forced savings. Renters pay monthly housing costs with no equity accumulation. Homeowners pay monthly costs that partially reduce their debt, gradually building ownership. However, home values can also decline, reducing or even eliminating equity in the short term. Renting versus buying analysis uses the mortgage calculator as a starting point. Compare the total monthly cost of homeownership (PITI plus maintenance plus HOA) against rent for a comparable property. Account for the opportunity cost of the down payment (what it would earn if invested instead), the tax benefit of mortgage interest deduction, the equity buildup from principal payments, and expected home price appreciation. In high-cost markets with low rent-to-price ratios, renting and investing the difference often wins financially. In affordable markets with reasonable home prices, buying typically builds more wealth over 7 or more years. Jumbo loans exceed the conforming loan limits set by Fannie Mae and Freddie Mac ($766,550 in most areas for 2024, higher in designated high-cost areas). Because jumbo loans cannot be sold to these government-sponsored enterprises, lenders take on more risk and typically charge higher interest rates (0.25% to 0.5% higher), require larger down payments (10% to 20% minimum), and demand higher credit scores (700 or above). Jumbo borrowers should compare offers from multiple lenders since pricing varies more than for conforming loans. Biweekly mortgage payments split your monthly payment in half and pay that amount every two weeks. Because there are 52 weeks in a year, you make 26 half-payments, which equals 13 full monthly payments instead of 12. That one extra payment per year goes entirely toward principal. On a $300,000 30-year loan at 6.5%, biweekly payments shorten the loan by about 4.5 years and save roughly $72,000 in interest. Not all lenders offer true biweekly payment programs. Some collect biweekly payments but only apply them monthly, which eliminates the benefit. Verify that your lender applies each biweekly payment immediately. Mortgage calculators help with the rent-versus-buy decision at each stage of life. A 25-year-old who moves frequently may prefer renting because transaction costs (closing costs, agent commissions) make buying worthwhile only if you stay at least 3 to 5 years. A 35-year-old settling in a career city may benefit from buying because the mortgage payment is fixed (unlike rent, which increases) and equity builds over time. A 55-year-old nearing retirement might pay off the mortgage early to reduce fixed expenses in retirement. Each scenario uses the same math but leads to different optimal decisions. Inflation affects mortgage math in a way that benefits borrowers. A fixed-rate mortgage locks in your payment in nominal dollars. If inflation runs at 3% per year, your $1,896 monthly payment is worth less in real purchasing power each year. After 10 years of 3% inflation, that same payment has the purchasing power of about $1,411 in today's dollars. After 20 years, it is equivalent to about $1,050. This inflation erosion of debt value is one reason financial advisors sometimes recommend keeping a mortgage even when you could pay it off, especially if the mortgage rate is low relative to inflation and investment returns. Investment property mortgages differ from primary residence mortgages. Interest rates are 0.5% to 0.75% higher. Down payment requirements are typically 20% to 25% minimum. Qualifying is harder because lenders may not count projected rental income at full value (typically 75% of expected rent). However, investment property mortgage interest is fully deductible against rental income, and depreciation provides additional tax benefits. The mortgage calculator helps determine whether the rental income covers the mortgage payment plus expenses, which is the basic test of investment property viability. The WebRecast mortgage calculator takes your loan amount, interest rate, and loan term, then outputs the monthly payment, total interest paid, and total cost of the loan. Use it to compare different scenarios: how much does the payment change with a larger down payment, a shorter term, or a lower interest rate? Run multiple scenarios to see the impact of each variable. These comparisons make the financial implications concrete and help you make the decision that best fits your situation.
Frequently asked questions
What formula is used?
Standard amortization: M = P[r(1+r)^n]/[(1+r)^n-1]
