Monthly Mortgage Payment Calculator

Calculate your exact monthly mortgage payment using the standard amortization formula — and understand precisely what portion goes to principal, interest, taxes, insurance, and PMI every single month.

What Makes Up Your Monthly Mortgage Payment?

Principal (P) — the debt repayment component: Each monthly payment includes a portion that directly reduces your outstanding loan balance. In early payments this portion is surprisingly small — on a $340,000 loan at 7% in month 1, only $363 of your $2,263 payment reduces the loan balance. The principal portion grows slowly with each payment as the interest portion decreases, but it takes many years before principal meaningfully outpaces interest.
Interest (I) — the cost of borrowing computed daily: Mortgage interest accrues daily on your outstanding balance. Each month, the lender multiplies your remaining balance by the daily rate (annual rate ÷ 365) and charges approximately 30 days of accrued interest. On a $340,000 balance at 7% annual rate, daily interest is $65.21 and a 30-day month accrues $1,956 in interest — meaning $1,956 of your $2,263 first payment is pure interest cost, not equity.
Property Tax escrow (T) — collected monthly, paid by the lender: Lenders typically require you to pay property taxes through an escrow account — one-twelfth of your annual tax bill is added to every monthly payment. If your annual property tax is $6,000, that's $500/month collected by the lender and held in escrow until the tax bill is due. This component does not amortize — it stays constant or rises with annual reassessment.
Insurance escrow (I) — homeowner's and mortgage insurance combined: Homeowner's insurance (typically $1,500–$3,000/year) is collected monthly via escrow alongside property tax. If your down payment was less than 20%, PMI (Private Mortgage Insurance) is also added — typically 0.5%–1.5% of the loan amount annually ($141–$425/month on a $340,000 loan). PMI cancels automatically when your equity reaches 22% under the Homeowners Protection Act.
The amortization formula M = P[r(1+r)^n]/[(1+r)^n-1] is the core calculation: This formula takes your loan principal (P), monthly interest rate (r = annual rate ÷ 12), and number of payments (n = years × 12) to compute the fixed monthly P&I payment that keeps the loan balance at exactly zero after the final payment. For a $300,000 loan at 6.75% for 30 years: r = 0.005625, n = 360, M = 300,000 × [0.005625 × (1.005625)^360] / [(1.005625)^360 − 1] = $1,945/month in principal and interest.

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How to Calculate Your Exact Monthly Mortgage Payment

Enter the loan principal (home price minus down payment): This is the amount you are actually borrowing — not the home's purchase price. On a $375,000 home with $75,000 down (20%), the loan principal is $300,000. This is the P in the amortization formula and the balance you pay interest on from day one.
Enter the annual interest rate as a decimal percentage: Use the interest rate (not the APR) for calculating the P&I payment — the APR includes fees spread across the loan term and is used for total cost comparison, not for computing individual payments. Your lender's loan estimate will show both figures; enter the interest rate field.
Enter the loan term in years: Standard US mortgages are 30 or 15 years, but 20 and 10-year terms exist. The term determines n (number of payments). A 30-year term means 360 monthly payments; 15 years means 180. Shorter terms mean higher P&I payments but dramatically less total interest paid.
Add property tax and insurance to see total PITI: Divide your annual property tax bill by 12 and add that figure. Divide your annual homeowner's insurance premium by 12 and add that too. If applicable, add your PMI estimate. The sum is your full PITI — the real number that comes out of your bank account each month.
Verify against your lender's quoted payment: Use the calculator to independently check any payment quote you receive. If the lender's number differs from yours by more than a few dollars on the P&I component, ask them to show their calculation — discrepancies may indicate different loan amounts, rates, or fee structures have been embedded in the estimate.

Real-World Use Case

Jennifer receives a Loan Estimate from her lender showing a monthly payment of $2,847 on a $385,000 loan at 6.875% for 30 years. She uses the monthly mortgage payment calculator to verify: plugging in P = $385,000, r = 6.875% ÷ 12 = 0.5729%, n = 360, the formula returns M = $2,530/month in principal and interest. Adding $512/month property tax escrow and $138/month homeowner's insurance escrow gives a verified PITI of $3,180/month — not $2,847. She calls her lender and discovers the quoted payment used an incorrect tax estimate and omitted the insurance escrow. The discrepancy of $333/month over 12 months is $3,996/year — information she needs for accurate budgeting. By independently verifying the lender's quote, she catches the error before signing and adjusts her budget accordingly.

Best Practices for Monthly Payment Accuracy

Always verify lender quotes independently using the amortization formula: Loan Estimates can contain errors in escrow estimates, incorrect rate assumptions, or missing components. Running the calculation yourself using the exact principal, rate, and term from your Loan Estimate takes two minutes and can reveal discrepancies worth hundreds of dollars per month. Lenders are required to provide accurate estimates but errors do occur, particularly in the escrow components.
Understand that extra payments permanently reduce future interest, not future payments: Making an extra $300 payment in month 6 does not reduce your required monthly payment — the fixed amortization schedule holds your required payment constant. What changes is the balance on which interest accrues next month, which slightly reduces the interest portion and increases the principal portion of subsequent payments, ultimately shortening the loan term. This is a powerful but widely misunderstood mechanic.
Model the payment difference between 6.5%, 7.0%, and 7.5% before locking your rate: On a $350,000 30-year loan: 6.5% = $2,213/month P&I; 7.0% = $2,329/month; 7.5% = $2,448/month. The 1% spread between 6.5% and 7.5% costs $235/month or $84,600 over the full term — quantifying this before rate lock decisions underscores why waiting a few weeks for better rates, or paying points to reduce the rate, can be worth significant money.
Include PMI in your payment projection until you reach 20% equity: PMI is often overlooked in monthly payment projections. On a $375,000 loan with 10% down ($337,500 loan balance), PMI at 0.9% annually adds $253/month to your payment for the first 7–8 years until your equity reaches 20%. Budget for the full PITI-plus-PMI figure from the start, not the post-PMI payment you'll eventually reach.
Use bi-weekly payment calculations to reduce your effective interest rate: Switching from monthly to bi-weekly payments (half your monthly payment every two weeks) results in 26 half-payments per year — the equivalent of 13 full monthly payments instead of 12. On a $325,000 loan at 7%, this one extra annual payment reduces the loan term by approximately 4.5 years and saves around $67,000 in total interest without increasing your monthly budget significantly.

Performance & Limits

Formula precision: Calculates payments using the full compound interest amortization formula with floating-point precision — results match bank-grade payment computations to the penny for standard fixed-rate mortgages.
P&I breakdown by payment: Generates a complete month-by-month schedule showing the exact principal paid, interest charged, and remaining balance for every payment from month 1 through final payoff — up to 360 payments for a 30-year term.
Extra payment integration: Models the effect of additional principal payments — monthly supplements, annual lump sums (such as tax refunds), or one-time payments — showing the recalculated payoff date and total interest saved after each extra payment scenario.
PITI component display: Breaks the total monthly cost into all five components (principal, interest, property tax, homeowner's insurance, PMI) on a single screen — enabling precise comparison with lender-issued Loan Estimates.
Rate comparison: Enter two or three rate scenarios simultaneously to see side-by-side monthly payment differences and total interest cost comparisons across different rate environments.

Common Mistakes to Avoid

Confusing the interest rate with the APR when computing your monthly payment: The APR (Annual Percentage Rate) is higher than the interest rate because it incorporates origination fees, points, and other closing costs amortized over the loan term. Using the APR in the payment formula will give you a higher computed payment than your actual contractual P&I amount — always use the stated interest rate (not APR) when running the amortization calculation to verify a quoted payment.
Assuming the monthly payment stays the same when you make extra principal payments: Standard fixed-rate mortgages do not automatically reduce your required monthly payment when you pay extra — the payment schedule is fixed. Extra payments reduce the loan balance (and therefore future interest charges), cutting the total number of payments and saving interest, but your required payment amount on your next statement remains unchanged. Only a formal loan recast resets your required payment downward.
Forgetting that escrow accounts are estimated, not fixed: Property tax and homeowner's insurance escrow amounts are re-evaluated annually by your lender. If property taxes rise or your insurance premium increases, your lender will adjust your monthly escrow collection — which raises your total payment even though your principal and interest component stays fixed. Budget for modest annual increases in your total PITI even on a fixed-rate mortgage.
Not accounting for the first month's payment being due 45–60 days after closing: Unlike rent (typically due the 1st of the month you're living there), mortgage payments are paid in arrears — your first payment covers the prior month's interest. If you close on March 15, your first full payment is typically due May 1, covering April's interest. This creates a deceptive lull that can cause cash flow surprises for new homeowners expecting an immediate payment obligation.

Privacy & Security

Client-side amortization engine: The full amortization formula executes in your browser's JavaScript engine — loan amounts, interest rates, and payment schedules are computed locally and never transmitted to external servers.
Zero data retention: Payment calculations, loan parameters, and PITI breakdowns are held only in browser memory for the current session and are discarded the moment you leave or refresh the page.
No lender referral or lead generation: This calculator does not share your loan data with mortgage lenders, brokers, or financial services companies — your inputs exist purely for your own calculation.
No account or identity required: Full access to all calculation features, amortization schedules, and payment breakdowns without providing any personal information or creating an account.

Frequently Asked Questions

What is the exact formula used to calculate a monthly mortgage payment?

The standard fixed-rate mortgage payment formula is M = P[r(1+r)^n] / [(1+r)^n − 1], where M is the monthly principal-and-interest payment, P is the loan principal (home price minus down payment), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (loan term in years multiplied by 12). For example: a $275,000 loan at 7.25% for 30 years gives r = 7.25% ÷ 12 = 0.6042%, n = 360, and M = 275,000 × [0.006042 × (1.006042)^360] / [(1.006042)^360 − 1] = $1,877/month in P&I. To this you add property tax and insurance escrow to arrive at your true total PITI payment. This formula is the same one banks use, and you can verify any lender quote by running it yourself.

Why is so much of my early mortgage payment interest instead of principal?

In the first month of a $350,000 mortgage at 7% for 30 years, your payment is $2,329. Of that, $2,042 is interest (350,000 × 0.07 ÷ 12) and only $287 reduces the loan balance. This front-loading of interest is not a lender trick — it is the mathematical result of applying a fixed percentage rate to a large outstanding balance. Because the balance is highest at the start, the interest charge is highest at the start. As you make payments and the balance slowly shrinks, less goes to interest each month and more goes to principal. By month 180 (year 15), the split is roughly $1,372 interest and $957 principal on the same 30-year loan. By month 300 (year 25), it flips to $537 interest and $1,792 principal.

How do I calculate how much extra payment I need to pay off my mortgage 5 years early?

To pay off a 30-year mortgage in 25 years, you need to make 300 total payments instead of 360 — effectively, you need a higher monthly payment that amortizes the same principal over fewer months. For a $325,000 loan at 6.875%, the standard 30-year payment is $2,136/month; to pay off in 25 years, recalculate with n = 300, which gives $2,295/month — an extra $159/month achieves the 5-year early payoff and saves approximately $57,000 in total interest. Alternatively, use the calculator's extra payment feature to find that a one-time lump-sum payment made early in the loan (e.g., $15,000 in year 2) can similarly shift the payoff date by 3–5 years depending on timing.

What is mortgage recasting and how does it differ from refinancing?

Mortgage recasting (also called re-amortization) is when you make a large lump-sum principal payment and your lender recalculates your monthly payment at the same interest rate and remaining term — permanently reducing your required monthly payment for the rest of the loan. Unlike refinancing, recasting does not change your interest rate or loan term, does not require a credit check or appraisal, and typically costs $150–$500 (vs. $3,000–$8,000 for a refinance). For example: if you receive a $50,000 inheritance and apply it to a $380,000 loan balance, recasting would reduce your required monthly payment by approximately $330/month at a 7% rate. Recasting is ideal when you want lower required payments but your rate is already competitive and you do not need a longer term.