How much house can your monthly budget really carry? A mortgage calculator answers that by turning a loan amount, rate, and term into one monthly number. It also shows how much of your money goes to interest over the life of the loan.
This free mortgage calculator works out your monthly principal and interest payment, total interest, total cost, and payoff date. It also builds a yearly amortization schedule. It is built for US home buyers, owners thinking about extra payments, and anyone comparing loan offers.
Table of Contents
- What This Mortgage Calculator Does
- How to Use the Calculator Step by Step
- The Mortgage Payment Formula
- Worked Example: A $320,000 Home Loan
- How to Read Your Results
- What Changes Your Mortgage Payment
- Limitations and Assumptions
- FAQs About the Mortgage Calculator
What This Mortgage Calculator Does
The tool runs in your browser and updates as you type. Here is what it gives you:
- Monthly Payment: your fixed principal and interest payment, rounded to the nearest dollar.
- Total Interest and Total Payment: what you pay the lender over the full loan.
- Payoff Date: the month and year the loan reaches a zero balance.
- Extra Monthly Prepayment: an optional amount added to every payment to pay the loan off sooner.
- Payment Summary: principal, total interest, total payment, and an interest to principal ratio. With an extra payment, it also shows the interest you save.
- Yearly Amortization Schedule: principal paid, interest paid, total paid, and ending balance for each calendar year.
- Copy Summary and Export Schedule: copy a one-line summary, or download the yearly schedule as a CSV file.
How to Use the Calculator Step by Step
- Type your Home Loan Amount ($). This is the price minus your down payment, not the full home price.
- Enter the Interest Rate (% per year) from your lender quote, such as 6.5.
- Set the Loan Tenure (Years). Most US buyers pick 30 or 15 years.
- Pick the Loan Start Date. The schedule and payoff date count forward from here.
- Add an Optional: Extra Monthly Prepayment ($) if you plan to pay more each month. Leave it at 0 otherwise.
- Results update live. You can also press Calculate, or press Reset to clear the inputs and set the start date to today.
Not sure of your loan amount yet? Start with the down payment calculator to see how much cash you need up front.
The Mortgage Payment Formula
The calculator uses the standard fixed-rate amortization formula. It is the same math US lenders use for principal and interest:
M = P × r × (1 + r)^n ÷ ((1 + r)^n - 1)
Loan Amount (P)&Monthly Rate (r)&Number of Payments (n)→Monthly Payment (M)
- M is the monthly principal and interest payment.
- P is the home loan amount.
- r is the annual rate divided by 12, then by 100. A 6.5% rate gives 0.005417.
- n is the term in years times 12, rounded to whole months.
Each month, interest equals the remaining balance times r. The rest of the payment, plus any extra prepayment, reduces the balance. If the rate is 0%, the payment is simply P divided by n.
Worked Example: A $320,000 Home Loan
Say you buy a $400,000 home and put 20% down. That leaves a $320,000 loan at 6.5% for 30 years, starting November 15, 2026. Here is what the tool shows, with and without an extra $200 each month.
| Result | No Extra Payment | Extra $200 per Month |
|---|
| Monthly Payment | $2,023 | $2,023 (plus $200 extra) |
| Total Interest | $408,142 | $302,714 |
| Total Payment | $728,142 | $622,714 |
| Payoff Date | Nov 2056 | Apr 2050 |
| Interest/Principal Ratio | 127.54% | 94.60% |
The exact payment is $2,022.62. In the first month, $1,733.33 goes to interest and only $289.28 goes to principal. Adding $200 a month cuts 79 payments and saves about $105,429 in interest.
How to Read Your Results
- Monthly Payment: the base principal and interest payment only. It does not include your extra prepayment.
- Total Interest: every dollar of interest paid until the balance hits zero.
- Total Payment: principal plus total interest, including any extra payments you made.
- Payoff Date: the start date moved forward by the number of payments it takes to clear the loan.
- Interest/Principal Ratio: total interest as a share of the loan. A ratio over 100 percent means you pay more in interest than you borrowed.
- Yearly Schedule: one row per calendar year. Unless the loan starts in January, the first and last rows are partial years, so they look smaller.
Watch the schedule over time. Early rows are mostly interest, while later rows are mostly principal. That shift is why extra payments in the early years save the most.
What Changes Your Mortgage Payment
Three inputs drive the result. The rate matters most over a long term. On the same $320,000 loan, a 15-year term raises the payment to $2,788. However, total interest drops to about $181,758, less than half the 30-year figure.
Your loan amount depends on price and down payment. A bigger down payment lowers both the payment and total interest. Use the house affordability calculator to set a price range that fits your income.
Your real monthly bill is usually higher than this result. Lenders often collect property tax, homeowners insurance, and PMI in an escrow account. Estimate the tax part with the property tax calculator, then add it on top.
Already have a loan? Compare a new rate with the refinance calculator. If you plan a large lump sum instead of monthly extras, try the mortgage recast calculator.
Limitations and Assumptions
- It covers principal and interest only. There are no fields for taxes, insurance, PMI, or HOA dues.
- It assumes a fixed rate for the whole term. It does not model adjustable-rate mortgages.
- There is no down payment field. Enter the loan amount after your down payment.
- Extra payments must be the same every month. One-time or yearly lump sums are not supported.
- Results round to whole dollars, and the schedule is yearly, not monthly.
- The Clear button empties the schedule but leaves the top results in place. Copy Summary leaves out the payoff date and extra payment.
FAQs About the Mortgage Calculator
Does This Mortgage Calculator Include Taxes and Insurance?
No. It shows principal and interest only. Add your monthly property tax, insurance, and any PMI to get your full housing payment.
Should I Enter the Home Price or the Loan Amount?
Enter the loan amount. Subtract your down payment from the price first, then type the result.
Can I Use My APR as the Interest Rate?
Use the note rate your lender quotes for the payment. APR adds fees, so it runs a bit higher. Check the full cost with the APR calculator.
How Much Do Extra Payments Save?
It depends on the rate, balance, and timing. On a $320,000 loan at 6.5%, $200 extra a month saves about $105,429 and ends the loan 79 months early.
Why Is Most of My Early Payment Interest?
Interest is charged on the remaining balance. The balance is highest at the start, so interest takes the biggest share then.
Can I Download the Amortization Schedule?
Yes. Press Export Schedule to save a CSV file with yearly principal, interest, total paid, and balance. It opens in Excel or Google Sheets.
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This calculator gives planning estimates only and is not financial advice. Reviewed for general accuracy by Prof. Dr. Khalil Mudassar, PhD.