Mortgage Payment Calculator
Calculate your mortgage principal and interest payment.
All calculations happen locally in your browser — nothing is uploaded, stored or tracked.
Enter loan amount, rate, term
The three inputs that determine the payment.
Add tax/insurance (optional)
For the full monthly picture.
Read the breakdown
Payment, first-month split, totals.
What Is a Mortgage Payment Calculator?
This calculator focuses on the core of any mortgage: the monthly principal and interest payment. It shows the first payment's exact split between interest and principal, the total interest over the term, and the total amount paid.
Optional property tax and insurance fields give the full monthly cost. The calculator is deliberately transparent about the numbers behind the payment.
The Formula
First month's interest = P × r; first month's principal = M − interest. After n payments the loan is fully repaid.
Your data never leaves your device.
Every calculation on this site runs in your browser using vanilla JavaScript. Nothing is uploaded, stored or tracked.
- 100% local, client-side calculations
- No data stored on any server
- No tracking, no analytics, no ads scripts
- Works offline once loaded
Frequently Asked Questions
What is included in a mortgage payment?
Principal, interest, and usually property tax and insurance held in escrow. This calculator separates them so you see each.
How much of my first payment goes to interest?
About the full month's interest on the balance — for a $300,000 loan at 6.5%, that is $1,625 of a ~$1,896 payment.
Why does the principal share grow over time?
Because interest is charged on the shrinking balance, leaving more of each fixed payment for principal.
What happens if I pay extra?
Extra payments go straight to principal, cutting total interest and shortening the term — see the extra payment calculators.
Is the rate monthly or annual?
Annual — the calculator divides it by 12 for the monthly rate, the standard convention.