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Principal and interest (P&I)

The two parts of every loan payment. Interest is the lender’s charge for that month, based on the current balance; principal is whatever remains of the payment, and it reduces the balance. The payment stays the same, but the split between the two shifts every month, which is what this calculator shows.

Amortization

Paying off a loan through equal scheduled payments that each cover that month’s interest plus part of the principal. Early payments are mostly interest because the balance is highest; as the balance falls, more of each payment goes to principal. By the last payment the balance reaches zero.

Amortization schedule

A payment-by-payment table showing, for each month, the payment, the interest portion, the principal portion and the remaining balance. It makes the shift from interest to principal visible and shows the balance at any future date — useful for planning a payoff or refinance.

First-payment interest

The interest portion of the first payment: the full loan amount times the annual rate divided by 12. On $25,000 at 7%, it is about $145.83 of a roughly $495 payment. It is the largest interest portion of the whole loan, because the balance is never higher than at the start.

First-payment principal

The part of the first payment that reduces the balance: the payment minus that month’s interest. On $25,000 at 7% over 5 years, about $349 of the first $495 payment goes to principal. Each later payment puts slightly more toward principal, because interest is charged on a smaller balance.

Monthly payment

The fixed amount due each month that repays the loan in full by the end of the term, calculated from the loan amount, rate and term. It stays constant on a fixed-rate loan even as its interest and principal parts change. Fees, insurance or rate changes on your actual loan could make it differ.

Remaining balance

The principal still owed after a given payment. It falls slowly at first and faster later, because more of each payment goes to principal over time. On longer loans, the balance can take well over half the term to fall to half the original amount.

Extra principal payment

Any amount paid above the scheduled payment and applied directly to the balance. Because future interest is charged on a smaller balance, it shortens the loan and lowers total interest; the earlier it is made, the larger the effect. Confirm the loan has no prepayment penalty and that the lender applies it to principal.

Total interest

The sum of all interest paid over the life of the loan if every payment is made on schedule — total payments minus the amount borrowed. Because interest is front-loaded, a large share of it is paid in the first part of the term.