What an amortization schedule shows
An amortization schedule is the row-by-row story of your loan. For each payment it records the total amount due, how much clears interest, how much reduces the principal, and what balance remains. The defining feature of an amortizing loan is that the payment stays fixed while the split between interest and principal shifts every month. Early on, most of your payment is interest; late in the loan, almost all of it is principal.
The payment formula
M = P × [r(1+r)n] / [(1+r)n − 1]
P is the loan principal, r the monthly rate (APR ÷ 12), and n the number of monthly payments (years × 12). After each payment, the new balance equals the old balance minus the principal portion, and next month's interest is charged on that smaller balance.
Worked example
On a $250,000 loan at 6.5% over 30 years, the fixed payment is about $1,580. In month one, interest is $250,000 × 0.065 ÷ 12 ≈ $1,354, so only ~$226 attacks the principal. By year 15 the balance is near $170,000 and the principal slice has grown past the interest slice. Over the full term you pay roughly $319,000 total — about $69,000 of it interest. Add just $100/month of extra principal and you shave years off the loan while saving tens of thousands in interest.
Reading the chart
The line chart plots the remaining balance month by month; it falls steeply once principal payments dominate. A shorter term (15 vs 30 years) produces a much faster drop and far less total interest, at the cost of a higher monthly payment. Use the schedule to find the month where you cross the break-even point between interest and principal.
5 tips to master your loan
- Pay extra early. Extra principal in the first years saves the most interest because the balance is largest then.
- Biweekly payments help. Paying half the monthly amount every two weeks yields 26 half-payments (one extra full payment) per year.
- Refinance when rates drop. A lower APR resets the schedule in your favor; compare with our Refinance Calculator.
- Round up the payment. Rounding $1,580 to $1,600 quietly shortens the term with no budgeting pain.
- Check the payoff row. The final balance should hit zero; if it shows a few cents, that is the last payment rounding.
Related calculators
Compare loan types with the Mortgage Calculator, see refinance savings with the Refinance Calculator, or model early payoff with the Loan Calculator. Browse all Finance tools.