Mortgage Calculator

How to Use the Mortgage Calculator

This mortgage calculator turns a home price, a down payment, an interest rate and a loan term into the numbers that really matter: your monthly payment, the total interest you will pay, and the full cost of the home. Everything runs instantly in your browser, so you can test as many scenarios as you like.

1. Enter the home price and your down payment. Type the purchase price, then choose whether the down payment is a dollar amount or a percentage of the price. Example: for a $300,000 home with a 20% down payment, enter 300000 as the price and 20 as the percentage — the calculator converts it to $60,000 and finances the remaining $240,000.

2. Set the interest rate and loan term. Enter the annual interest rate quoted by your lender and the term in years. Common terms are 15 and 30 years. Example: a $240,000 loan at 6% over 30 years gives a principal-and-interest payment of about $1,439 per month and roughly $278,000 of interest over the life of the loan.

3. Add optional housing costs. If you want the true monthly cost of owning the home, enter the annual property tax, annual home insurance and any monthly HOA fees. Example: $3,600 of tax per year ($300/month), $1,200 of insurance per year ($100/month) and $50 of HOA dues bring the total monthly payment to about $1,889.

4. Read the results. The summary cards show the principal-and-interest payment, the total monthly payment, the loan amount, total interest and the total cost of the home. A principal-versus-interest bar and a yearly amortization table show how the balance falls over time. Use the copy button to save the summary.

What Is a Mortgage Payment?

A mortgage is a loan used to buy a property, and the property itself acts as collateral for the lender. The loan is repaid through a fixed monthly payment over a set number of years. Each payment is split into two parts: interest, which is the lender's charge for the money you have borrowed, and principal, which reduces the outstanding balance. Early payments are mostly interest; later payments are mostly principal. The calculator uses the standard amortization formula: PMT = P x [r(1+r)^n] / [(1+r)^n - 1], where P is the loan principal, r is the monthly interest rate (the annual rate divided by twelve) and n is the total number of monthly payments. When the rate is zero the payment is simply the principal divided by the number of payments. Real ownership costs go beyond the loan. Property tax, home insurance and HOA dues are usually collected together with the mortgage payment, which is why lenders talk about PITI: principal, interest, taxes and insurance. Estimating all of these together gives a far more realistic picture of what a home will cost each month than looking at the loan payment alone.

Common Applications

1. Budgeting a first home purchase. A buyer considering a $300,000 home with 20% down at 6% sees a monthly principal-and-interest payment of about $1,439, then adds taxes and insurance to check that the full payment fits their budget.

2. Comparing 15-year and 30-year terms. On the same $240,000 loan at 6%, a 15-year term raises the monthly payment to about $2,025 but cuts total interest from roughly $278,000 to about $124,600 — a difference of more than $150,000.

3. Measuring the effect of a larger down payment. Moving from 10% to 20% down on a $300,000 home reduces the loan from $270,000 to $240,000 and lowers the monthly payment by about $180 at 6%.

4. Shopping between lenders. Two offers with the same price and term but different rates can be compared side by side to see exactly how much a 0.5% difference costs over 30 years.

5. Testing the impact of HOA and taxes. A buyer weighing two neighborhoods with different property tax rates can add each rate to the calculator to see how far it pushes the true monthly cost.

How Your Down Payment Changes Everything

The down payment is the single largest lever you control when buying a home. Because it directly reduces the loan amount, every extra dollar you put down lowers both your monthly payment and the total interest you pay over the term. On a $300,000 home, going from 10% down to 20% down removes $30,000 from the loan.

There is another benefit that is easy to miss: private mortgage insurance. Many lenders require it when the down payment is below 20%, and it is added straight onto your monthly payment. Crossing the 20% threshold can therefore reduce your monthly cost twice — once through the smaller loan and once by removing the insurance requirement. The calculator lets you see the loan math clearly so you can judge whether saving a larger deposit is worth delaying your purchase.

Reading the Amortization Summary

Amortization is the slow shift from paying mostly interest to paying mostly principal. In the first year of a 30-year loan, the vast majority of each payment covers interest, because the balance is still close to its original size. As the years pass, the balance shrinks, less interest accrues each month, and more of the fixed payment attacks the principal.

The yearly breakdown table shows this transition year by year. Watching the interest column shrink while the principal column grows is the clearest way to understand why extra payments early in a loan save so much: they remove principal at the moment when interest is most expensive. Even a modest extra amount paid in the first years can cut thousands of dollars of interest and shorten the loan considerably.

What a Mortgage Payment Really Includes: P&I, Taxes, and Insurance

A mortgage payment usually is not a single number. The core is principal and interest (P&I): principal repays what you borrowed, and interest is the lender's charge on the balance. For a fixed-rate loan, P&I follows the amortization formula M = P × [ r(1 + r)^n ] ÷ [ (1 + r)^n − 1 ], where M is the monthly P&I, P the loan amount, r the monthly rate (the annual rate divided by 12), and n the number of monthly payments. On top of that, many borrowers pay into an escrow account for property taxes and homeowners insurance, and sometimes mortgage insurance or HOA dues. Those extras are not part of the interest calculation and can change from year to year.

An example makes the scale clear. Borrow $300,000 at a 6.5% annual rate for 30 years. The monthly rate is 0.065 ÷ 12 ≈ 0.0054167 and n = 360, so P&I comes to about $1,896. Total payments over the full term reach roughly $682,600, of which about $382,600 is interest. These are estimates that exclude taxes, insurance, and fees.

15-Year vs 30-Year Mortgages: A Trade-Off in Two Directions

Choosing a term is a trade-off between monthly cash flow and total cost. On the same $300,000 at 6.5%: a 30-year loan asks about $1,896 a month and charges roughly $382,600 in interest, while a 15-year loan (n = 180) asks about $2,614 a month and charges roughly $170,400. The 15-year route costs about $718 more each month but saves about $212,000 in interest and clears the debt fifteen years sooner. In reality, 15-year loans often carry a slightly lower rate than 30-year loans, which would widen that saving; holding the rate constant simply isolates the effect of term.

Neither choice is universally better. A 30-year loan leaves more room in the monthly budget, while a 15-year loan builds equity faster and costs less overall. Many borrowers take the 30-year payment for flexibility and then add extra payments voluntarily. A calculator can show the arithmetic of each path, but it cannot tell you which fits your life. Figures are estimates only and are not financial advice.

Extra Payments and Biweekly Payments: How Much They Save

Interest is charged on the outstanding balance, so extra payments reduce the balance early and cut the interest charged in every later month. On the $300,000, 6.5%, 30-year example, adding $200 to each monthly payment would finish the loan in roughly 23 years and lower total interest from about $382,600 to about $279,000 — a saving near $103,000. A single $10,000 payment made in the first year typically saves tens of thousands of dollars in interest and shortens the term by a few years, because that balance no longer accrues interest for decades.

Biweekly plans work on the same idea. Paying half the monthly P&I every two weeks produces 26 half-payments, which is 13 full payments a year instead of 12 — effectively one extra payment annually. On a 30-year loan that usually trims the term to roughly 25–26 years. Before you do this, check for a prepayment penalty, and confirm that extra money is applied to principal rather than treated as an early next installment. Treat savings figures as illustrations, not promises.

Common Mistakes and Edge Cases

Several traps are common. Shopping by monthly payment alone hides total cost: a longer term lowers the payment but raises the interest paid. The interest rate differs from the annual percentage rate (APR), which folds in many lender fees and gives a fuller yearly picture — though still not the entire cost. Escrow items such as taxes and insurance can rise, increasing the total payment even when P&I is fixed. A small down payment may add mortgage insurance. And an adjustable-rate mortgage's initial rate does not last forever; later payments follow the index and margin.

Some cases fall outside the standard formula entirely: balloon loans, interest-only periods, and negative amortization. Fees, points, closing costs, and prepayment penalties sit outside P&I, and rounding can make a calculator's totals differ slightly from a lender's. To compare offers fairly, look at the P&I, the APR, the total interest, and the total amount repaid together. Everything here is an educational estimate, not a lending offer or financial advice; for a real mortgage, rely on your Loan Estimate and consider a qualified professional.

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