Extra payment

A payment above the required monthly amount. Properly applied, it reduces principal directly and saves the future interest that amount would have accrued.

Reviewed May 2026.

An extra payment is the simplest way to pay off a loan faster. Whether monthly ($100/month extra) or one-time (a $5,000 lump sum), the math works the same: extras go to principal after the regular interest+principal split, shrinking the balance.

The critical word: 'properly applied.' By default, some servicers (especially for student and personal loans) apply extras as 'advance the next due date' rather than principal reduction. The dollars don't vanish — overpayments still flow through fees → interest → principal — but paid-ahead status can blunt the calculator's assumed savings: the due date moves earlier, the borrower may pay less attention next month, and the principal-reduction benefit you modeled may not materialize unless you keep paying on schedule AND tell the servicer to apply extras to principal (not advance the due date). Submit a written standing instruction for principal-only treatment, then verify on the next statement that the balance dropped by the full extra amount.

Lump sums save slightly more per dollar than monthly extras spread over the same period, because the money hits earlier and eliminates interest sooner. But monthly extras are easier to maintain — flexibility often beats math.

PayoffMath angle. Extras are the entire premise of PayoffMath. Two facts decide what a given extra is worth: how early in the loan it lands, and whether the servicer actually applies it to principal rather than rolling it into next month's due date.

Why it matters. An extra payment that gets booked as 'paid ahead' rather than principal-only doesn't shrink the balance the way the calculator's projection assumes. Same dollars in, very different payoff outcome — the difference shows up on the next statement.

Common mistake. Sending an extra in the same envelope as the regular payment without specifying principal-only treatment. Many servicers default to advancing the next due date in that case. A written standing instruction (or the lender's online 'apply to principal' flag) is what guarantees the routing.

Try the debt payoff strategy calculator → — compare where the next extra dollar produces the most savings across multiple loans, not just the one you're tempted to attack.

Worked example

Example: $20,000 loan at 9% APR over 60 months. Adding $100/month in extras pays it off in 47 months instead of 60 (13 months saved) and saves $1,183 in interest. A $5,000 lump sum at month 1 pays it off in 41 months and saves $1,950.

See also

Sources and review

Reviewed May 2026. Glossary entries are plain-language definitions, not legal definitions. For account-specific rules, your loan documents control.

Definition by James L. Wu. Plain-language gloss, not a legal definition. For terms that show up in your loan paperwork, the governing language is in your loan documents. See the editorial policy for sourcing.