Amortization Calculator

Add extra monthly principal to watch the schedule shrink. The yearly table rolls months into calendar-year totals so a multi-year loan stays readable; the monthly table lists every installment.

This is the same engine as the payment and loan calculators. It does not add mortgage escrow or auto-loan taxes — only principal and interest on a fixed-rate installment loan.

Interest each month is the current balance times the monthly rate. Principal is the payment minus that interest. Extra principal is applied after the required payment.

Read across: payment, principal, interest, balance. Early rows are interest-heavy. Later rows are principal-heavy. Extra principal makes that shift happen sooner.

These figures match the calculator for $10,000 at 6% over 36 months with no extra.

Some loans have prepayment penalties or apply extra to future installments instead of principal. Confirm with the servicer before you treat these savings as guaranteed.

Interest is always the current balance times the monthly rate. On a new $10,000 balance at 6%, that is $50 before a single dollar of principal is paid. The required $304.22 therefore sends only $254.22 to principal. A year later the balance is lower, so the same $304.22 sends more to principal. Extra principal does not change that rule; it just makes the balance drop sooner so the interest column shrinks faster. If you only need the payment and a yearly roll-up, the payment calculator is enough. Open this page when you want every month written out, or when you are comparing two extra-payment amounts on the same loan.

The monthly table can be long — 360 rows on a 30-year term — which is why the yearly summary sits above it. Cents on the screen are rounded; the engine keeps full precision so the last payment can land on a zero balance instead of a leftover penny. That last installment is often a few cents different from the regular payment, and that is expected.