Break any fixed-rate loan down into its full principal-and-interest payment schedule — with support for extra monthly, yearly, and one-time payments.
Amortization is just the plan for erasing a debt through a series of equal, scheduled payments. Every payment is the same size, but the mix inside it isn't: part covers the interest the lender is owed for that period, and the rest chips away at the amount you originally borrowed. Because the amount you still owe keeps shrinking, the interest portion keeps shrinking with it — which means, even though the payment itself never changes, more of each check goes toward the balance as the loan matures.
Interest is charged only on the balance still outstanding, so it's largest in the loan's first year and smallest in its last. Picture two loans side by side, both $200,000 at 6% — one just starting, one with $20,000 left. The first accrues roughly $1,000 in interest that month; the second, only about $100. Same rate, wildly different interest bill, purely because of how much principal remains. That's the entire mechanism behind the curve you see in the schedule above: interest fading, principal rising, payment flat.
An extra payment goes straight to the principal — it never touches interest. That means your required monthly payment doesn't drop; instead, the balance the next month's interest is calculated on is smaller, which snowballs into a shorter loan and a smaller total interest bill. A one-time payment nudges the balance down once; a recurring extra payment compounds that effect every single month it's active.
This calculator fits any fixed-rate, fixed-term loan that's paid down with level payments — mortgages, auto loans, student loans, personal loans. It doesn't fit revolving debt like credit cards, where the balance and minimum payment move independently, or interest-only and balloon loans, which don't spread principal evenly across the term in the first place.
No — your scheduled payment stays exactly the same. What changes is how much of the loan is left, so it gets paid off sooner and costs less in total interest.
Because interest is calculated on the full remaining balance, and early on that balance is close to the full loan amount. As the balance falls, so does the interest charged against it, and the principal share grows to fill the gap.
They show the same underlying numbers at different resolutions — the annual view totals each year's interest and principal into one row, while the monthly view breaks every single payment out individually so you can see exactly how the balance moves month to month.
Yes — this calculator supports up to ten separate one-time extra payments, each on its own date, on top of an optional recurring monthly or yearly extra payment.
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