How is a monthly mortgage payment calculated?

Principal and interest follow the amortization formula M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the loan amount, r is the monthly interest rate, and n is the number of monthly payments. Property tax and home insurance are added on top for the full PITI payment.

What does PITI stand for?

PITI is principal, interest, taxes, and insurance, the four components that typically make up a total monthly housing payment. The calculator adds optional tax and insurance to the standard principal-and-interest figure.

How does the loan term affect total interest?

Longer terms reduce the monthly payment but increase total interest, because principal is paid down more slowly. A 30-year mortgage at the same rate as a 15-year usually produces more than double the total interest.

Is my mortgage data sent to a server?

All calculations run locally in your browser as JavaScript. The numbers you enter never leave your device.

Mortgage calculator

Mortgage calculator is a finance tool that estimates monthly mortgage payments from loan amount, rate, and term. It uses the standard amortization formula, supports tax and insurance add-ons for full PITI, and shows the year-by-year amortization schedule. The tool runs in your browser.

Currency

Home price

Down payment

Interest rate (% per year)

Term (years)

Property tax (% per year, optional)

Home insurance ($ per year, optional)

Formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where P = loan amount, r = monthly rate, n = months

Dedicated pages

Mortgage calculations for specific scenarios.

Monthly Mortgage Payment Calculator

Calculate your monthly mortgage payment with principal, interest, property tax, and home insurance. Instant results, runs in your browser.

30-Year Mortgage Calculator

Calculate monthly payments and total interest for a 30-year fixed mortgage. See full lifetime cost in seconds, all in your browser.

Mortgage Amortization Schedule

Generate a full mortgage amortization schedule showing principal and interest paid each year and the remaining balance. Free, in-browser.

How to calculate a mortgage payment

Enter the home price and choose your down payment as a percentage or fixed amount.
Enter the annual interest rate and select a term in years.
Optionally add property tax percentage and yearly home insurance.
Review the monthly payment, total interest, and year-by-year amortization schedule.

Technical specification

Algorithm or formula: Standard amortization formula M = P[r(1+r)^n] / [(1+r)^n - 1], where P is principal, r is monthly interest rate, and n is total number of monthly payments. PITI adds monthly property tax and insurance on top.
Browser API or library: Pure JavaScript arithmetic; no external library. Uses Number primitives for all calculations.
Input limits: Home price up to 100,000,000. Rate 0%–30%. Term 1–50 years. Down payment 0%–100%.
Output: Monthly principal-and-interest payment, monthly PITI, total interest paid over the loan, and a year-by-year amortization table showing the running balance, principal, and interest each year.
Known limitations: Fixed-rate amortization only; ARM, balloon, and interest-only mortgages are not modeled. Tax and insurance are treated as constant over the loan term.

Frequently asked questions

How is a monthly mortgage payment calculated?: Principal and interest follow the amortization formula M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the loan amount, r is the monthly interest rate, and n is the number of monthly payments. Property tax and home insurance are added on top for the full PITI payment.
What does PITI stand for?: PITI is principal, interest, taxes, and insurance, the four components that typically make up a total monthly housing payment. The calculator adds optional tax and insurance to the standard principal-and-interest figure.
How does the loan term affect total interest?: Longer terms reduce the monthly payment but increase total interest, because principal is paid down more slowly. A 30-year mortgage at the same rate as a 15-year usually produces more than double the total interest.
Is my mortgage data sent to a server?: All calculations run locally in your browser as JavaScript. The numbers you enter never leave your device.

Calculations are estimates for informational purposes only. Consult a financial professional for advice.

Reviewed and tested May 25, 2026.