Start a mortgage payment calculation with four inputs: home price, down payment, annual interest rate, and loan term. Those figures are enough to estimate the loan’s fixed principal-and-interest payment, total interest, total paid, and year-by-year amortization schedule. In the Mortgage Calculator, home price minus down payment becomes the loan principal, while the rate and term determine the monthly payment under a standard fixed-rate amortization model. You can then add optional property tax, homeowners insurance, and HOA dues to estimate a fuller monthly housing cost. Everything runs locally in your browser, so financial inputs are not uploaded or stored. The result is designed for general information and planning rather than as a final lender quote. It assumes that the rate remains fixed for the entire term and that interest compounds monthly. It also excludes private mortgage insurance, points, closing costs, adjustable rates, extra payments, and escrow adjustments. This makes the calculator useful as a first budgeting estimate: enter the four loan inputs, read the P&I result, and then add the housing costs that the base payment does not include. Confirm exact terms and figures with a licensed lender or mortgage professional before making a decision.
Prepare the Four Core Inputs
Prepare a clean set of assumptions before entering anything. You need the purchase price, the amount you plan to put down, the annual interest rate you want to model, and the number of years you want the loan to remain outstanding. Home price and down payment should describe the same transaction, the rate should be expressed as an annual percentage, and the term should be measured in years.
Keep the first calculation focused on the loan itself. P&I stands for principal and interest: the portion of the housing payment that repays the mortgage. Taxes, insurance, and HOA dues can be added afterward. Separating these categories makes it easier to understand why the payment shown by a mortgage calculator may be lower than the total amount you expect to send for housing each month.
| Input or setting | What the calculator does with it | What it affects |
|---|---|---|
| Home price and down payment | Subtracts the down payment from the home price | Loan principal |
| Annual interest rate | Converts the annual percentage into a monthly rate | Monthly interest and total interest |
| Loan term | Converts years into the total number of monthly payments | Payment amount and amortization period |
| Property tax, insurance, and HOA | Adds optional monthly housing-cost estimates | PITI plus HOA |
Calculate Your First Mortgage Estimate
- Open the Mortgage Calculator. It runs locally in your browser.
- Enter the home price and down payment. The calculator subtracts the down payment from the price to establish the principal you would borrow.
- Type the annual interest rate. Enter the yearly rate as a percentage. The calculator performs the conversion to a monthly rate as part of its fixed-rate calculation.
- Choose a loan term. Select 15 years or 30 years, or enter a custom number of years when you need a different amortization period.
- Read the monthly payment, total interest, and total paid. The headline monthly payment is the estimated fixed P&I amount. Total interest shows the estimated interest over the full term, while total paid includes the loan principal and scheduled interest.
- Expand the amortization schedule. Review the year-by-year breakdown showing how the scheduled payment is divided between principal and interest.
- Add optional housing costs when needed. Enter a property tax rate, annual homeowners insurance premium, and monthly HOA dues to produce an estimated monthly PITI-plus-HOA figure.
Understand the Fixed-Rate Calculation
The estimate uses the standard fixed-rate mortgage amortization formula. First, the principal is calculated as P = home price − down payment. The calculator converts the annual percentage to a monthly interest rate: r = (annual rate percentage ÷ 100) ÷ 12. It then converts the term to the number of monthly payments: n = years × 12.
The fixed monthly principal-and-interest payment is calculated as M = P × r(1 + r)^n ÷ ((1 + r)^n − 1). When the annual interest rate is exactly 0%, the formula becomes M = P ÷ n, dividing the principal into equal monthly payments.
Total interest is the sum of all scheduled payments minus the original principal. Total paid represents the principal plus that estimated interest over the selected term. These totals describe the loan repayment schedule; optional taxes, insurance, and HOA dues are shown separately rather than changing the mortgage’s payoff.
Add Taxes, Insurance, and HOA Costs
The base P&I result answers only one part of the monthly housing-cost question. Property taxes and homeowners insurance are not components of the loan itself, while HOA dues are another recurring housing expense. Adding them provides a more useful planning figure for the cash needed to operate the home.
- Property tax: The monthly estimate is home value multiplied by the tax rate, divided by 12.
- Homeowners insurance: The annual premium is divided by 12 to produce a monthly estimate.
- HOA dues: The monthly amount is added as entered.
P&I means principal and interest. PITI adds property tax and homeowners insurance. When monthly HOA dues are included, the display reflects PITI plus HOA. These additions raise the amount of cash sent each month but do not accelerate principal repayment or change the amortization schedule. This distinction is why lenders evaluate PITI rather than relying on P&I alone.
See How the Loan Balance Changes
Expand the amortization schedule after reading the headline payment. It provides a year-by-year view of how each scheduled payment is split between principal and interest. That view helps you see how the loan composition changes over its full term rather than treating every monthly payment as entirely interest or entirely principal.
The underlying schedule is constructed one month at a time. Interest is applied to the outstanding balance, and that interest amount is subtracted from the fixed payment. The remaining amount reduces the principal and, in turn, lowers the balance. This process continues until the balance reaches zero at the final payment. Because the calculation assumes a fixed rate, the displayed split follows that fixed-rate model for the entire selected term.
Match Each Result to Your Question
Different outputs answer different budgeting questions. Use each figure for the purpose it was designed to serve rather than treating one number as the complete cost of homeownership.
| Calculator output | Question it answers |
|---|---|
| Monthly P&I | How much is scheduled each month to repay principal and interest? |
| Total interest | How much interest is estimated over the selected fixed-rate term? |
| Total paid | How much principal and scheduled interest is paid across the full loan term? |
| Amortization schedule | How is the payment divided between principal and interest over time? |
| PITI plus HOA | What is the estimated monthly housing outflow after adding the optional costs? |
Confirm Assumptions and Know What Is Missing
A calculator result is only as complete as its assumptions. This tool follows standard conventions for U.S. fixed-rate mortgages: the rate stays fixed for the full term and interest compounds monthly. It is designed for estimates rather than individualized underwriting or financial advice.
Several important items are outside the calculation:
- Private mortgage insurance, or PMI
- Points and other closing costs
- Adjustable interest rates
- Extra principal payments
- Changes in escrow amounts
The optional property tax, insurance, and HOA figures also follow simple budgeting conversions rather than a quote for future escrow payments. A useful second pass is to follow how to verify your mortgage payment calculator result. Record the four inputs and optional add-ons so you can explain exactly which assumptions produced the estimate.
Use the Estimate as a Planning Baseline
Use P&I to understand the scheduled repayment of the loan, then use PITI plus HOA to plan the broader monthly housing outflow. Review total interest and total paid together because a longer term can change the payment and lifetime interest trade-off. Use the amortization schedule to inspect how principal and interest change over time.
Because the calculator does not upload or store your inputs, write down the home price, down payment, annual rate, term, and optional costs if you expect to reproduce or compare the estimate. Bring those assumptions to a licensed lender or mortgage professional when you need exact figures, available costs, or terms for a real transaction. Starting with four numbers establishes a useful estimate; checking the formulas, adding housing costs, and confirming the exclusions turns that estimate into a responsible budgeting starting point.
For a deeper look, see Troubleshoot a Car Loan Payment Calculator.