An amortization schedule looks like a wall of numbers, but every row follows the same three steps. Once you can follow one row, you can answer practical questions from the table: how much you still owe after five years, why the balance barely moved in year one, and when your payment starts doing more good than harm.
The example below is a 250,000 loan at a fixed 6.5% nominal annual rate over 30 years, run through Calculation Guide's amortization engine with no extra payment. The regular payment is 1,580.17 a month. Twelve rows are shown out of 360.
| Month | Payment | Interest | Principal | Balance after payment |
|---|---|---|---|---|
| 1 | 1,580.17 | 1,354.17 | 226.00 | 249,774.00 |
| 2 | 1,580.17 | 1,352.94 | 227.23 | 249,546.77 |
| 3 | 1,580.17 | 1,351.71 | 228.46 | 249,318.31 |
| 12 | 1,580.17 | 1,340.33 | 239.84 | 247,205.69 |
| 60 | 1,580.17 | 1,269.33 | 310.84 | 234,027.44 |
| 120 | 1,580.17 | 1,150.34 | 429.83 | 211,940.32 |
| 180 | 1,580.17 | 985.79 | 594.38 | 181,397.85 |
| 240 | 1,580.17 | 758.25 | 821.92 | 139,163.21 |
| 300 | 1,580.17 | 443.61 | 1,136.56 | 80,760.41 |
| 348 | 1,580.17 | 107.16 | 1,473.01 | 18,310.96 |
| 359 | 1,580.17 | 16.98 | 1,563.19 | 1,571.66 |
| 360 | 1,580.17 | 8.51 | 1,571.66 | 0.00 |
What each column in the schedule means
- Month is the payment number, not a calendar date. Payment 1 is usually due about a month after the loan funds; the exact date comes from your note.
- Payment is the fixed principal-and-interest amount. On a mortgage bill, taxes, insurance and mortgage insurance may be added on top, but they never appear in these columns.
- Interest is the opening balance for that month times the monthly rate. Here the monthly rate is 6.5% ÷ 12 = 0.541667%.
- Principal is whatever is left of the payment after interest. It is the only part that reduces what you owe.
- Balance is the opening balance minus that month's principal. It becomes the next row's opening balance.
Month 1: 250,000 × 0.065 ÷ 12 = 1,354.17 interest. 1,580.17 − 1,354.17 = 226.00 principal. 250,000 − 226.00 = 249,774.00 owed.
Check month 2 the same way: 249,774.00 × 0.065 ÷ 12 = 1,352.94. Interest fell by 1.23 because the balance fell by 226, and 226 × 0.541667% ≈ 1.22. That small drop is handed to principal, which is why the principal column creeps up by roughly a unit or two each month in the early years.
Why early payments are mostly interest
The payment is fixed, but interest is calculated on the balance. At the start the balance is the full loan, so interest takes 1,354.17 of the 1,580.17, about 86%. Nothing about the lender's priorities changes over time; the balance simply gets smaller, so the same rate produces less interest and more of the fixed payment is left for principal.
In the first year this borrower pays 16,167.73 in interest and only 2,794.31 in principal. In the final year the split reverses: 651.08 interest and 18,310.96 principal. The principal portion of a single payment grows about sevenfold across the life of the loan.
How front-loaded a schedule is depends on the rate and the length of the loan together. A 25,000 car loan at 7% over 5 years has a 495.03 payment, and its first month's interest is 145.83, under 30% of the payment. A long, higher-rate loan spends far more of its early life covering interest. The same arithmetic in reverse is why extra principal payments save so much interest early in a long loan.
Amortization CalculatorBuild the full month-by-month schedule for your own balance, rate and term, with or without an extra monthly payment.Three questions the schedule answers
How much will I still owe if I sell or refinance?
Read the balance column at that month. After 60 payments here, the borrower has paid 94,810.20 but still owes 234,027.44. Only 15,972.56 of what they paid reduced the debt. That gap matters if you expect to move in five years: sale proceeds must cover that balance plus selling costs, which is one reason the rent-versus-buy break-even often lands later than people expect.
When does principal overtake interest?
Scan down until the principal column first exceeds the interest column. In this loan that happens at payment 233, about 19 years and 5 months in. The balance does not reach half the original amount, 125,000, until payment 257. On a 30-year loan, the second half of the debt is repaid in less than 9 years.
What does the loan really cost?
Add the interest column. Over 360 payments it totals 318,861.22, so the borrower repays 568,861.22 for a 250,000 loan. The Loan Payment calculator shows that total directly if you do not need the rows.
Why your lender's schedule may differ slightly
Calculation Guide's engine keeps full precision through every row and rounds only for display, so adding the displayed cents can be off by a cent or two from the totals. A lender usually rounds each payment and each balance to the cent, and may adjust the last payment to clear what remains. Some loans accrue interest daily, so a month with 31 days costs a little more than one with 28, and paying a few days late or early shifts the split. If your statement disagrees by more than small change, ask the servicer which method applies.
What a standard schedule does not show
- Variable rates. The schedule assumes one fixed rate. When an adjustable rate resets, the lender recalculates the payment and every later row changes.
- Escrowed costs. Property tax, home insurance and mortgage insurance can be collected with the payment but do not reduce the balance. See the mortgage payment breakdown for those lines.
- Fees and APR. Origination charges are not in the rows, so the interest column is not the full cost of borrowing.
- Flat-rate quotes. A loan priced on a flat rate does not follow these rows at its quoted rate; convert it to a reducing-balance rate before comparing.
- Missed or partial payments. Unpaid interest, late fees and how a servicer applies partial payments are outside the model.