The short answer: an amortization schedule shows how each payment is divided between interest, principal and remaining balance. For a fixed-rate mortgage, the payment can stay the same while the interest share usually falls over time.
The mortgage calculator on this site includes a yearly and monthly amortization schedule for the loan amount, fixed annual rate and term you enter.
How fixed-rate payment math becomes a schedule
The calculator first finds the level monthly principal-and-interest payment. Then it applies each payment to the current balance:
- Interest is calculated from the outstanding balance and monthly rate.
- The rest of the payment reduces principal.
- The next month starts with the new lower balance.
This repeats until the final payment, which is adjusted to end the balance at $0.00 after rounding.
Why early payments include more interest
Interest is based on the outstanding balance. At the beginning of the loan, the balance is near the original principal, so interest takes a larger share of each payment. As principal is repaid, the balance falls and more of the same payment goes toward principal.
This is why a shorter term often costs less interest overall: the balance is reduced faster.
Worked example
For a $100,000 loan at 6.00 percent for 30 years, this site’s mortgage engine estimates a monthly principal-and-interest payment of $599.55 and total interest of $115,838.19.
| Year | Payments that year | Principal paid | Interest paid | Ending balance |
|---|---|---|---|---|
| 1 | $7,194.61 | $1,228.01 | $5,966.59 | $98,771.99 |
| 10 | $7,194.61 | $2,104.44 | $5,090.16 | $83,685.72 |
| 20 | $7,194.61 | $3,828.82 | $3,365.79 | $54,003.59 |
| 30 | $7,194.61 | $6,966.14 | $228.47 | $0.00 |
The payment is steady, but the principal share rises as the balance gets smaller.
What can change the schedule
This site’s schedule models a fixed-rate loan without extra payments. A real schedule can differ if the loan has an adjustable rate, extra principal payments, skipped payments, fees, escrow changes or lender-specific rounding.
Use the schedule as a planning view, then compare with your actual loan documents.
Sources and methodology
Examples on this page use this site's tested mortgage utilities. External sources support consumer-protection context and terminology; they do not replace lender documentation.
Planning disclaimer
This guide and its examples are for education and planning only. They are not mortgage approval, preapproval, a rate quote, tax advice, or lender advice.