Mortgage amortization
calculator.
See the full month-by-month breakdown of a mortgage: every dollar of interest, when you cross from mostly-interest to mostly-principal, and exactly how much time and interest an extra payment saves. Defaults to today's 30-year rate verify×DON'T TRUST, VERIFYClaim: The default rate is the latest Freddie Mac 30-year fixed average (6.43%, 2026-07-02).Verify at: FRED MORTGAGE30US ↗Stamped from data/macro.json at every build. Edit it to your quoted rate..
Principal and interest only. Taxes, insurance, PMI, and HOAHomeowners Association (HOA)An organization in some residential communities that sets rules and charges monthly fees for shared maintenance. are not included. Your numbers stay in your browser.
By year
| YEAR | INTEREST PAID | PRINCIPAL PAID | BALANCE |
|---|
On a 30-year loan, most of your early payments are interest, not principal. That is not a scam, it is how amortization works: interest accrues on the balance, which starts high. Extra principal early in the loan is where the biggest interest savings hide.
What this tool assumes
- Payment covers principal and interest only. Property tax, homeowners insurance, PMI, and HOA dues are real costs this figure excludes; your actual monthly outlay will be higher.
- The rate is fixed for the whole term. Adjustable-rate mortgages are not modeled.
- Extra payments are applied to principal every month starting immediately. The biweekly option approximates the standard "one extra payment a year" effect.
- The default rate is the latest Freddie Mac 30-year average, stamped from data/macro.json. Use the rate you were actually quoted.
Methodology and questions
How is the monthly payment calculated?
The standard amortization formula: M = P × r(1+r)^n / ((1+r)^n − 1), where P is the loan amount, r is the monthly rate (annual rate / 12), and n is the number of months. Each month, interest is the balance times r; the rest of the payment reduces principal.
Should I pay extra or invest the difference?
It depends on your rate versus your expected return. Paying down a 7% mortgage is a guaranteed 7% return; investing might beat it, or not. Work the tradeoff in the pay off debt or invest calculator.
Why is so much of my early payment interest?
Because interest is charged on the outstanding balance, which is largest at the start. As the balance falls, the interest portion shrinks and the principal portion grows. The crossover point is visible in the chart above.
Not financial advice. Principal and interest only. Your numbers stay in your browser.