Mortgage Calculator
Calculate your monthly mortgage payment and see exactly how much of each payment goes toward principal versus interest. Enter your home price, down payment, interest rate, and loan term to get a complete breakdown. Understand your total cost of homeownership including property taxes, insurance, and HOA fees.
Reviewed by the SparkCalc editorial team · May 2026
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How to use this calculator
- Enter the home price and your down payment. The calculator subtracts the down payment to find your loan amount (the principal).
- Set the loan term — most U.S. mortgages are 30 or 15 years — and the annual interest rate from your lender or rate quote.
- Add property tax, homeowners insurance, and any HOA fees to see your full monthly housing cost, not just principal and interest.
- Review the monthly payment and the amortization schedule to see how much goes to interest versus principal over time.
- Try adding an extra monthly payment to see how many years and how much interest you could save.
How We Calculate This
This calculator uses the standard amortization formula: M = P[r(1+r)^n]/[(1+r)^n-1], where M is monthly payment, P is principal, r is monthly interest rate, and n is number of payments. Property taxes, insurance, and other expenses are added separately.
Methodology last reviewed: May 2026. How SparkCalc works
Sources: U.S. CFPB — Understand the different kinds of loans available
How your monthly mortgage payment is calculated
A fixed-rate mortgage payment comes from a standard amortization formula: M = P × [ 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 12), and n is the total number of monthly payments (years × 12). The result is the fixed amount that pays your loan off exactly at the end of the term. Because interest is charged on a shrinking balance, the split between interest and principal changes every month even though the total payment stays the same.
What's actually included in your payment
Lenders describe the full payment as PITI: Principal, Interest, Taxes, and Insurance. Principal and interest are set by your loan. Property taxes and homeowners insurance are usually collected monthly into an escrow account and paid on your behalf. If your down payment is below 20%, PMI is added, and homes in some communities also carry HOA dues. Looking only at principal and interest can understate your true monthly cost by hundreds of dollars — this calculator lets you include the other pieces so the number is realistic.
Why extra payments save so much
Every extra dollar you pay goes straight to principal, which means you stop paying interest on that dollar for the entire remaining life of the loan. On a 30-year mortgage, modest extra payments early on can shave years off the term and save tens of thousands in interest. Use the extra-payment option above to see the effect for your specific loan before committing — even an extra $100 a month is often surprisingly powerful.
Key terms
- Principal
- The amount you borrow — the home price minus your down payment. Your monthly payment slowly pays this balance down.
- Interest rate vs APR
- The interest rate is the cost of borrowing the principal. The APR is broader: it folds in lender fees and points, so it is the better number for comparing loan offers.
- Amortization
- The schedule that splits each payment between interest and principal. Early payments are mostly interest; later payments are mostly principal.
- PMI (private mortgage insurance)
- An extra monthly charge lenders usually require when your down payment is under 20%. It protects the lender, not you, and can often be removed once you reach 20% equity.
- Escrow
- An account your lender uses to collect property tax and insurance alongside your payment, then pays those bills on your behalf.
- Down payment
- The cash you pay upfront. A larger down payment lowers your loan amount, your monthly payment, and often your interest rate, and can remove PMI.
Frequently Asked Questions
How is my monthly mortgage payment calculated?
Your monthly mortgage payment is calculated using the loan amount, interest rate, and loan term. The formula accounts for the amortization of the loan, meaning early payments are mostly interest while later payments are mostly principal. Additional costs like property tax and insurance are added to get your total monthly payment.
How does the loan term affect my payment?
A shorter loan term means higher monthly payments but less total interest paid. A 15-year mortgage typically has lower interest rates than a 30-year mortgage, and you will pay significantly less interest over the life of the loan.
How much house can I afford?
A common guideline is that your total monthly housing payment should not exceed 28% of your gross monthly income (the "front-end ratio"). Your total debt payments including the mortgage should not exceed 36% of gross income (the "back-end ratio").
Should I put down 20%?
Putting down 20% reduces your loan amount and monthly payment. With less than 20% down, many lenders require Private Mortgage Insurance (PMI) which adds to your monthly costs. Consider your savings, emergency fund, and whether you could invest the difference.
How can I lower my monthly payment?
You can lower your monthly payment by: making a larger down payment, choosing a longer loan term, shopping for a lower interest rate, or buying a less expensive home. Refinancing later when rates drop is another option.
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You might also find these calculators helpful: Rent vs Buy Calculator, Home Affordability Calculator, and Loan Comparison Calculator.
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This calculator provides estimates for educational purposes only. Actual mortgage terms, rates, and payments may vary. Consult with a mortgage lender for accurate quotes and pre-approval.