Mortgage Calculator
Calculate your monthly mortgage payment, total interest paid, and full amortization schedule.
What this calculator does
This mortgage calculator works out what a home loan costs you each month and across its full term. Enter the home price, your down payment, the interest rate you have been quoted, and the length of the loan, and it returns the monthly principal and interest payment, the total interest paid over the life of the loan, and a complete amortization schedule showing how each payment splits between interest and principal.
The amortization schedule is the part worth studying. A single monthly figure tells you whether you can afford the payment; the schedule tells you what you are actually buying — how long you spend paying mostly interest, when the balance starts falling meaningfully, and how much the loan costs in total rather than per month.
When to use it
Most people reach for a mortgage calculator at three moments. Before house hunting, to work backward from a payment you are comfortable with to a price range that produces it. While comparing lender quotes, to convert competing rate and fee combinations into monthly and lifetime numbers you can rank. And when considering overpayments or a refinance, to see whether the interest saved justifies the cost.
It is equally useful for the decision to wait. Running today's rate against a rate you expect in a year, at a price you expect in a year, turns a vague instinct about timing into two numbers you can compare directly.
Understanding the inputs
Home price and down payment together determine the loan amount, which is what interest is actually charged on. A down payment below 20 percent generally triggers PMI, so it is worth testing figures either side of that threshold.
Enter the annual interest rate as quoted — the calculator converts it to a monthly rate internally. Use the note rate rather than the APR here, since APR folds in fees and would overstate the interest portion of the payment. Loan term is the repayment period in years, typically 30 or 15 in the US. The extra monthly payment field applies additional money to principal each month, which is the fastest lever for cutting total interest.
How is this calculated?
M = P[r(1+r)^n]/[(1+r)^n-1] where P is the principal loan amount, r is the monthly interest rate, and n is the number of payments.
A worked example
Take a $450,000 home with a 10 percent down payment of $45,000, leaving a $405,000 loan at 6.5 percent over 30 years. The monthly principal and interest works out at roughly $2,560, and total interest across the term comes to about $516,000 — more than the original loan.
In month one, close to $2,190 of that payment is interest and only around $370 reduces the balance. Shortening the term to 15 years raises the monthly payment to roughly $3,530 but cuts total interest to about $230,000. That is the tradeoff in concrete terms: around $970 more per month buys back roughly $286,000.
Limitations and assumptions
This calculator models principal and interest on a fixed-rate loan. It does not include property taxes, homeowners insurance, PMI, HOA dues, closing costs, or discount points, and it assumes the rate never changes — so figures for an adjustable-rate mortgage are valid only through the initial fixed period.
It also assumes payments arrive on schedule and are applied monthly. For a binding number, use the Loan Estimate your lender is required to provide, which includes every fee. Use this calculator for what it is good at: comparing scenarios quickly and understanding the shape of the loan.
Common Questions
- How is a mortgage payment calculated?
- Your monthly payment comes from three numbers: the principal you borrow, the interest rate, and the term. The amortization formula spreads them into a single payment that stays level for the life of a fixed-rate loan. Every payment covers the interest accrued that month first, and whatever is left reduces the principal.
- Does this include taxes and insurance?
- No. This shows principal and interest only — the part determined by your loan. Property taxes, homeowners insurance, PMI, and any HOA dues are added by your lender into an escrow payment. Those extras commonly add 20 to 30 percent on top, so budget for the full PITI figure rather than the number shown here.
- Should I choose a 15-year or 30-year mortgage?
- A 15-year term costs substantially more each month but far less overall, because you are paying interest for half as long and usually at a lower rate. A 30-year keeps the monthly payment affordable and leaves room in your budget. Run both terms above — the total interest column is where the difference shows up starkly.
- How much does the interest rate actually matter?
- More than most buyers expect. On a $400,000 loan over 30 years, one percentage point changes the payment by roughly $250 a month and the total interest by around $90,000. Shopping two or three lenders is one of the highest-value hours you can spend in the buying process.
- What is PMI and when do I stop paying it?
- Private mortgage insurance protects the lender, not you, and is normally required when your down payment is under 20 percent. It typically runs 0.5 to 1.5 percent of the loan each year. You can request cancellation once you reach 20 percent equity, and it must be removed automatically at 22 percent under federal rules.
- Is it worth making extra payments toward principal?
- Usually yes, and earlier is much better than later. Extra money applied to principal removes all the future interest that balance would have generated. Use the extra payment field above to see the effect. Confirm with your lender that overpayments are applied to principal rather than held toward the next scheduled payment.
- Why does so little of my early payment reduce the balance?
- Interest is charged on the outstanding balance, which is at its largest at the start. In the first years of a 30-year loan most of each payment covers interest and only a small slice touches principal. The ratio shifts steadily over time — the amortization schedule above shows exactly when the crossover happens.
- How much should I put down?
- Twenty percent avoids PMI and secures better pricing, but it is not mandatory — conventional loans go to 3 percent and FHA to 3.5 percent. The tradeoff is a larger loan, a higher payment, and mortgage insurance. Weigh that against the cost of waiting to save while prices and rates move.
- Does this work for adjustable-rate mortgages?
- Only for the initial fixed period. This calculator assumes one rate for the entire term, so an ARM's payment after the first adjustment is not modeled. Use it to understand the introductory payment, then ask your lender for the worst-case payment at the rate cap before committing.
- How accurate is this estimate?
- The principal and interest figure is mathematically exact for a fixed-rate loan. What it excludes are closing costs, points, escrow, and any lender fees rolled into the loan. Treat it as an accurate answer to a narrow question — reliable for comparing scenarios, not a substitute for a Loan Estimate.
Related calculators
- Mortgage Payoff CalculatorSee what sending extra money toward principal each month does to your payoff date and the interest you avoid.
- Bi-Weekly Mortgage Payment CalculatorCompare a standard monthly schedule against paying half your payment every two weeks, and see the interest and years it saves.
- Mortgage Comparison CalculatorPut two loans side by side on the same home price and down payment, and compare monthly payment, total interest and total cost.