Amortization Schedule Calculator (Full Payment Table)
A monthly payment figure hides the part that matters: how little of your early payments touch the balance. This builds the full amortization schedule — every month's principal, interest, and remaining balance — and shows what a single extra payment each month does to your interest bill and payoff date.
How this calculation works
The payment is fixed by the standard amortization formula: payment = P × r ÷ (1 − (1 + r)^−n), where P is the loan amount, r the monthly rate (annual ÷ 12 ÷ 100), and n the number of months. The payment never changes; what changes is how it is split.
Each month, interest is charged on the balance that is currently outstanding — balance × r. Whatever is left of your payment after that interest reduces the principal. Because the balance falls, next month's interest is slightly smaller and slightly more of the same payment goes to principal.
That is why the early years feel like standing still. On a 30-year loan at 6.5%, the first payment is roughly 85% interest; the crossover where principal finally exceeds interest arrives around year 18.
An extra payment is applied entirely to principal, so it removes not just that amount from the balance but every future month of interest that amount would have generated. The saving compounds, which is why a modest extra payment shortens the term far more than it appears it should.
Worked example
What the schedule reveals that a payment figure hides
Two loans with identical monthly payments can cost wildly different amounts, and only the schedule shows why. The table below tracks the same 300,000 loan at 6.5% over 30 years and shows how much of the balance is actually gone at each milestone.
| After | Paid so far | Of which interest | Balance remaining | % of loan repaid |
|---|---|---|---|---|
| 1 year | 22,754 | 19,382 | 296,628 | 1.1% |
| 5 years | 113,772 | 94,946 | 281,174 | 6.3% |
| 10 years | 227,544 | 185,169 | 257,625 | 14.1% |
| 15 years | 341,316 | 266,505 | 225,189 | 24.9% |
| 20 years | 455,088 | 334,908 | 179,820 | 40.1% |
| 25 years | 568,860 | 383,932 | 115,072 | 61.6% |
| 30 years | 682,633 | 382,633 | 0 | 100% |
Extra payments: small input, disproportionate output
The reason an extra payment punches above its weight is that it removes future interest, not just present principal. Paying 200 extra in month 1 of a 6.5% loan avoids every month of interest that 200 would have accrued for the next 29 years — which is why 200 a month, 72,000 in total over 25 years, saves roughly 76,000 in interest and clears the loan five years early.
Timing matters more than size. The same extra payment made in year 1 saves several times what it saves in year 20, because there is far more remaining interest to cancel. If you can only make extra payments for a limited period, making them as early as possible is strictly better. A single extra payment a year — funded by a bonus or by paying half your payment every two weeks, which produces 13 monthly payments a year — typically takes four to five years off a 30-year term without any change in monthly budgeting.
How to read your own schedule
Three checks are worth doing on the table this calculator generates. First, find your crossover month — the first row where principal exceeds interest — because that is the point the loan starts working for you. Second, look at the balance at the moment you realistically expect to sell or refinance, not at the end of the term; that number, not the 30-year total, determines your equity. Third, compare total interest against the amount borrowed. When interest exceeds the principal, as it does on any 30-year loan above about 5%, a shorter term or extra payments deserve serious consideration.
Then verify the schedule against your lender's statement. Yours may differ slightly for legitimate reasons: some lenders use actual day counts (365/360 or actual/actual) rather than equal twelfths, the first period may be longer or shorter than a month depending on the closing date, and any escrowed tax or insurance sits outside amortization entirely. A discrepancy of a few units per month is normal; a discrepancy in the balance is worth a phone call.