Mortgage Amortization Schedule Calculator
A mortgage amortization schedule breaks down every payment over the life of your loan, showing exactly how much goes to interest and how much reduces your principal balance. For a standard fixed-rate mortgage, your monthly payment remains constant, but the split between interest and principal shifts over time. Early in the loan, the majority of each payment covers interest on the large outstanding balance. As the balance falls, interest charges decrease and more of each payment chips away at principal. Enter your loan details below to see your monthly payment, total interest paid, and the first 12 months of your amortization schedule.
Mortgage amortization formula
M = P * r(1+r)^n / ((1+r)^n - 1)
Interest(month) = Balance * r
Principal(month) = M - Interest(month)
Where P is the original loan principal, r is the monthly interest rate (annual rate / 12 / 100), and n is the total number of monthly payments (years * 12). Each month's interest is computed on the remaining balance before that payment.
How to read your amortization schedule
- The monthly payment stays constant for the life of a fixed-rate mortgage.
- Payment 1 has the highest interest charge because the balance is at its peak.
- The interest-to-principal ratio shifts gradually each month as the balance declines.
- Total interest equals the sum of all interest charges over the loan term.
- Paying extra toward principal on any given month reduces all future interest charges.
Mortgage amortization: frequently asked questions
What is mortgage amortization?
Amortization is the process of paying off a loan through regular scheduled payments. Each payment covers interest accrued since the last payment, with the remainder reducing the principal balance. Early payments are mostly interest; later payments are mostly principal.
How is the monthly payment calculated?
The monthly payment uses the formula M = P * r(1+r)^n / ((1+r)^n - 1), where P is the loan principal, r is the monthly interest rate (annual rate divided by 12), and n is the total number of payments.
Why does my interest payment decrease over time?
Each month, interest is charged only on the remaining principal balance. As you make payments, the balance decreases, so less interest accrues. This means more of each successive payment goes toward principal.
What happens if I make extra principal payments?
Extra principal payments reduce the outstanding balance immediately, which lowers the interest charged in subsequent months and shortens the loan term. See our Mortgage Extra Payment Calculator for the projected savings.
Does the amortization schedule change if I refinance?
Yes. Refinancing creates a new loan with a new amortization schedule based on the new balance, rate, and term. You restart the process where early payments are again mostly interest.
Official sources
- Consumer Financial Protection Bureau: Owning a Home.
- HUD: Buying a Home.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.