Calculate Mortgage Payments
Estimate monthly principal, interest, taxes, and insurance. Adjust home price, rate, term, and down payment to see how they affect total cost.
Examples
Example 1 -- Typical 30-year mortgage
Input: $400,000 home, 6.5% rate, 30-year term, 20% down ($80,000)
- Loan amount: $320,000
- Monthly payment: $2,023
- Total interest over 30 years: $408,031
- Total cost (principal + interest): $728,031
The total interest exceeds the original loan amount -- more than doubling the cost over 30 years.
Example 2 -- Same home, 15-year term
Input: $400,000 home, 6.5% rate, 15-year term, 20% down ($80,000)
- Loan amount: $320,000
- Monthly payment: $2,789
- Total interest over 15 years: $182,046
- Total cost (principal + interest): $502,046
The monthly payment is $766 higher, but you save $225,985 in total interest compared to the 30-year term.
Example 3 -- Lower down payment (10%)
Input: $400,000 home, 6.5% rate, 30-year term, 10% down ($40,000)
- Loan amount: $360,000
- Monthly payment: $2,275
- Total interest over 30 years: $459,035
Putting 10% less down increases total interest by $51,004 over the life of the loan. A down payment under 20% also typically requires PMI (not included in this estimate).
The Mortgage Payment Formula
The standard formula for a fixed-rate mortgage monthly payment:
M = P x [r(1 + r)n] / [(1 + r)n - 1]
- M -- monthly payment (principal & interest)
- P -- loan principal (home price minus down payment)
- r -- monthly interest rate (annual rate / 12, as a decimal)
- n -- total number of payments (loan term in years x 12)
Worked example
$300,000 loan at 6% for 30 years:
- P = 300,000
- r = 0.06 / 12 = 0.005
- n = 30 x 12 = 360
- M = 300,000 x [0.005 x (1.005)360] / [(1.005)360 - 1]
- M = 300,000 x [0.005 x 6.02258] / [6.02258 - 1]
- M = 300,000 x 0.030113 / 5.02258
- M = $1,798.65 per month
Over 360 payments, you pay $647,515 total -- of which $347,515 is interest.
How Interest Rate Affects Total Cost
On a $300,000 loan for 30 years, here is how different rates change the outcome:
| Interest Rate | Monthly Payment | Total Interest | Total Paid |
|---|---|---|---|
| 5.0% | $1,610 | $279,767 | $579,767 |
| 5.5% | $1,703 | $313,212 | $613,212 |
| 6.0% | $1,799 | $347,515 | $647,515 |
| 6.5% | $1,896 | $382,633 | $682,633 |
| 7.0% | $1,996 | $418,527 | $718,527 |
| 7.5% | $2,098 | $455,157 | $755,157 |
Each 0.5% increase in rate adds approximately $35,000--$37,000 in total interest on a $300,000 loan over 30 years.
15-Year vs. 30-Year Mortgage
The loan term has the biggest impact on total cost after the loan amount itself. Here is a side-by-side comparison for a $300,000 loan at 6.5%:
| Feature | 15-Year | 30-Year |
|---|---|---|
| Monthly payment | $2,613 | $1,896 |
| Total interest paid | $170,356 | $382,633 |
| Total cost (P + I) | $470,356 | $682,633 |
| Interest savings | $212,277 saved with 15-year | |
| Extra monthly cost | $717 more per month for 15-year | |
The 15-year term costs $717 more per month but saves $212,277 in total interest. It also builds equity faster -- you own the home outright in half the time.
Note: Choosing the right term depends on your budget, financial goals, and overall financial situation. This comparison shows the mathematical difference -- it is not a recommendation. Consider consulting a financial advisor for personalized guidance.
What This Calculator Does Not Include
While this calculator includes estimated property taxes and insurance, your actual monthly housing cost may also include:
- PMI (Private Mortgage Insurance): Required when the down payment is less than 20%. Usually costs 0.5%--1.5% of the loan amount per year. On a $360,000 loan, that could add $150--$450 per month until the loan-to-value ratio reaches 80%.
- HOA fees: If the property is part of a homeowners association. Can range from $50 to $500+ per month.
- Maintenance and repairs: A common estimate is 1%--2% of the home's value per year.
- Closing costs: Typically 2%--5% of the loan amount, paid upfront at closing.
When budgeting, add these costs to the estimate from this calculator for a more realistic picture of total monthly housing costs.
How Down Payment Affects Your Mortgage
The down payment reduces the loan amount, which affects monthly payment, total interest, and whether PMI is required. Here is the impact on a $400,000 home at 6.5% for 30 years:
| Down Payment | Loan Amount | Monthly P&I | Total Interest | PMI Likely? |
|---|---|---|---|---|
| 5% ($20,000) | $380,000 | $2,402 | $484,537 | Yes |
| 10% ($40,000) | $360,000 | $2,275 | $459,035 | Yes |
| 15% ($60,000) | $340,000 | $2,149 | $433,533 | Yes |
| 20% ($80,000) | $320,000 | $2,023 | $408,031 | No |
| 25% ($100,000) | $300,000 | $1,896 | $382,529 | No |
The jump from 5% to 20% down saves $76,506 in total interest and eliminates the PMI requirement.
Common Mistakes
- Only looking at the monthly payment: A lower monthly payment over 30 years can cost far more in total interest than a higher payment over 15 years. Always check total cost, not just the monthly number.
- Ignoring taxes, insurance, and PMI: The principal-and-interest payment is often only 60%--80% of the true monthly housing cost. Budget for the full picture.
- Assuming the interest rate is the only cost: Closing costs (typically 2%--5% of the loan amount), origination fees, and points also affect the total cost. Compare the APR (Annual Percentage Rate), which includes fees, not just the interest rate.
- Not comparing loan terms: A 30-year mortgage feels affordable month to month, but the total interest can exceed the original loan amount. Run the numbers for both 15- and 30-year terms before deciding.
- Forgetting that rates change daily: Mortgage rates fluctuate. The rate you see today may not be the rate you lock in. Get quotes from multiple lenders and compare on the same day.
- Maxing out the budget: Being approved for a certain loan amount does not mean you should borrow that much. Leave room for maintenance, emergencies, and other financial goals.
Frequently Asked Questions
How is a monthly mortgage payment calculated?
The formula is M = P x [r(1+r)n] / [(1+r)n - 1], where P is the loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of payments (years x 12). This calculates principal and interest only. Actual monthly costs also include property taxes, insurance, and possibly PMI.
How much does a down payment affect the monthly payment?
Directly. The down payment reduces the loan amount, which lowers both the monthly payment and total interest. On a $400,000 home at 6.5% for 30 years, going from 10% down to 20% down reduces the monthly payment by $252 and saves $51,004 in total interest over the life of the loan.
What is the difference between a 15-year and 30-year mortgage?
A 15-year mortgage has higher monthly payments but drastically lower total interest. For a $300,000 loan at 6.5%, the 15-year costs $717 more per month but saves $212,277 in interest. It also means you own the home free and clear 15 years sooner.
What is PMI and when is it required?
PMI (Private Mortgage Insurance) is typically required when the down payment is less than 20% of the home price. It protects the lender -- not the borrower -- against default. PMI usually costs 0.5%--1.5% of the original loan amount per year. It can be removed once the loan-to-value ratio reaches 80%, either through payments or home value appreciation.
What costs does this calculator not include?
This calculator shows principal, interest, taxes, and insurance. It does not include PMI (if down payment is under 20%), HOA fees (if applicable), closing costs, or maintenance. These can add $200--$1,000+ per month depending on location and loan details.
How does the interest rate affect total mortgage cost?
Significantly. On a $300,000 loan for 30 years, each 1% increase in rate adds roughly $70,000 in total interest. At 5%, total interest is $279,767. At 7%, it is $418,527 -- a difference of $138,760.
What is the mortgage payment formula?
M = P x [r(1 + r)n] / [(1 + r)n - 1]. M is the monthly payment, P is the loan principal, r is the monthly interest rate (annual rate / 12), and n is the total number of monthly payments (term in years x 12).
How much of my payment goes to interest vs. principal?
In the early years, most of each payment covers interest. On a $300,000 loan at 6.5% for 30 years, the first payment splits roughly $1,625 to interest and $271 to principal. This ratio gradually reverses over the life of the loan -- a process called amortization.
What is APR vs. interest rate?
The interest rate is the cost of borrowing the principal. The APR (Annual Percentage Rate) includes the interest rate plus other loan costs like origination fees, discount points, and certain closing costs, expressed as a yearly rate. APR gives a more complete picture of the loan's true cost and is useful for comparing offers from different lenders.
Does this calculator store my financial data?
No. All calculations run entirely in your browser using JavaScript. No financial data, inputs, or results are sent to any server. Nothing is stored or logged.
Related Tools
- Loan Amortization Schedule -- see a month-by-month breakdown of principal and interest
- Loan Calculator -- calculate payments for any fixed-rate loan
- Down Payment Calculator -- find how much to save for your down payment
- Compound Interest Calculator -- see how savings grow over time
- How Loan Amortization Works -- understand why early payments are mostly interest
- How Mortgage Payments Work -- complete guide to mortgage payment math
Privacy & Limitations
- Client-side only. No data is sent to any server. No cookies, no tracking of financial inputs.
- Estimates only. This calculator includes principal, interest, property taxes, and homeowners insurance. It does not include PMI, HOA fees, or closing costs. Add those separately when budgeting.
- Fixed-rate loans only. This calculator assumes a fixed interest rate for the entire term. Adjustable-rate mortgages (ARMs) have rates that change over time and require different calculations.
- Not financial advice. This tool provides mathematical estimates for educational purposes. Mortgage decisions involve many personal and financial factors. Consider consulting a qualified financial advisor or mortgage professional.
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Mortgage Calculator FAQ
How is a monthly mortgage payment calculated?
The monthly payment formula is M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). This calculates principal and interest only — actual payments also include property taxes, insurance, and possibly PMI.
How much does a down payment affect the monthly payment?
The down payment directly reduces the loan amount, which lowers both the monthly payment and total interest. On a $400,000 home at 6.5% for 30 years, a 10% down payment ($40,000) gives a $2,275/month payment with $459,035 total interest. A 20% down payment ($80,000) gives a $2,023/month payment with $408,031 total interest — saving $51,004 in interest.
What is the difference between a 15-year and 30-year mortgage?
A 15-year mortgage has higher monthly payments but much lower total interest. For a $300,000 loan at 6.5%: a 30-year term costs $1,896/month with $382,633 total interest; a 15-year term costs $2,613/month with $170,356 total interest. The 15-year saves $212,277 in interest but requires $717 more per month.
What is PMI and when is it required?
PMI (Private Mortgage Insurance) is typically required when the down payment is less than 20% of the home price. It protects the lender (not the borrower) against default. PMI usually costs 0.5% to 1.5% of the original loan amount per year. It can be removed once the loan-to-value ratio reaches 80% through payments or home appreciation.
What costs are not included in a basic mortgage calculator?
A basic mortgage calculator shows only principal and interest. Actual monthly housing costs also include property taxes (varies by location, often 0.5%–2.5% of home value per year), homeowners insurance ($1,000–$3,000+ per year), PMI (if down payment is under 20%), and HOA fees (if applicable). These additional costs can add $500–$1,500+ per month depending on location.
How does the interest rate affect total mortgage cost?
Interest rate has a large impact on total cost. On a $300,000 loan for 30 years: at 5% the total interest is $279,767; at 6% it is $347,515; at 7% it is $418,527. Each 1% increase in rate adds roughly $70,000 in total interest over the life of the loan.
Should I get a 15-year or 30-year mortgage?
A 15-year mortgage saves significantly on total interest and builds equity faster, but requires higher monthly payments. A 30-year mortgage has lower monthly payments, providing more cash-flow flexibility. The right choice depends on your budget, financial goals, and comfort level with the monthly payment. This is a personal financial decision — consider consulting a financial advisor.
What is the mortgage payment formula?
M = P × [r(1 + r)^n] / [(1 + r)^n − 1]. M is the monthly 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).
How much of my mortgage payment goes to interest vs principal?
Early in the loan, most of the payment covers interest. On a $300,000 loan at 6.5% for 30 years, the first payment is $1,896 — of which $1,625 is interest and only $271 is principal. By payment 180 (halfway), $988 goes to interest and $908 to principal. In the final payment, nearly the entire amount goes to principal. This gradual shift is called amortization.
Does this calculator store my financial data?
No. All calculations run entirely in your browser using JavaScript. No financial data, inputs, or results are sent to any server. Nothing is stored or logged.