How to Use This Tool
An amortization schedule answers a question the monthly payment figure hides: where is the money actually going? On a typical 30-year mortgage at 6.25%, the first payment is roughly 85% interest. You can make twelve payments, hand over more than twenty thousand dollars, and find the balance has moved by about three thousand. That is not a scam; it is how interest on a declining balance works. But almost nobody is shown it before they sign.
Filling in the four fields
Enter the loan amount, the annual rate, and the term in years. The payment appears immediately, using the standard amortizing formula shown in the diagram above. The fourth field — extra per month — is the interesting one. Add even a small amount and watch two numbers move: total interest falls, and the payoff date moves closer. The reason the effect is so large is that every extra dollar goes entirely to principal, and principal removed early stops accruing interest for every remaining month of the term.
Reading the chart and the table
The stacked chart shows each year's payments split into interest and principal. The crossover point — where principal finally overtakes interest — is worth finding, because it is much later than most people assume. On a 30-year loan at typical rates it falls somewhere around year eighteen.
Press Show full schedule for the row-by-row detail. Switch to monthly rows if you need to check a specific statement, or keep yearly rows for planning. The CSV export opens directly in Excel or Google Sheets if you want to model scenarios the tool does not cover.
Things this calculator deliberately does not include
- Property tax, insurance and escrow. Your actual mortgage payment is usually larger than this figure. This tool models the loan itself so the interest maths stays visible.
- Variable rates. The schedule assumes the rate holds for the whole term. On a tracker or ARM, treat the output as the current-rate scenario and re-run it when the rate resets.
- Fees rolled into the balance. If arrangement fees were added to the loan, enter the total amount borrowed rather than the amount you received.
One practical warning about extra payments: confirm with your lender that they are applied to principal rather than held as a prepayment of next month's instalment. The two are treated identically by some lenders and very differently by others, and only the first produces the saving shown here.
