An extra loan payment does two things: it reduces principal now and prevents that principal from generating interest in every later month. The benefit compounds over the remaining term, which is why a modest recurring extra payment can remove several payments at the end. The exact result depends on the balance, annual rate, required payment, timing, fees, and whether the lender actually applies the extra amount to principal.
A worked five-year example
Consider a $25,000 loan at 6% APR with 60 monthly payments. The standard payment is $483.32. Using monthly interest of 0.06 ÷ 12 and rounding only for display, the baseline schedule costs about $3,999 in interest. The same loan changes like this when every extra dollar is applied to principal:
| Extra each month | Paid off in | Total interest | Interest saved |
|---|---|---|---|
| $0 | 60 months | $3,999 | — |
| $50 | 54 months | $3,558 | $441 |
| $100 | 49 months | $3,206 | $793 |
| $200 | 41 months | $2,680 | $1,319 |
These are model results, not a lender quote. Real loans may accrue interest daily, round at different points, or include fees. Use the Loan Payoff Calculator with your own figures, then compare its estimate with your statement.
Monthly extra versus a lump sum
Earlier principal reduction usually saves more interest than the same dollars paid later. A $1,200 lump sum today begins lowering interest immediately; twelve $100 extras spread through the year reduce principal gradually. That does not mean a lump sum is always the better household decision. Keep an emergency reserve and compare the guaranteed loan rate with other uses for the money. For high-rate debt, principal reduction is often compelling; for a low fixed rate, liquidity may matter more.
Check how the lender applies it
Label an extra payment for principal when the servicer permits it, then inspect the next statement. Some systems advance the due date or hold money for a future installment instead of reducing principal as intended. Keep making the regular payment unless the lender confirms otherwise. Also check the contract for a prepayment penalty, especially before a large lump sum or full payoff.
A payoff quote is not the same as the balance shown online. The Consumer Financial Protection Bureau explains that a payoff amount can include interest through the intended payoff date, unpaid fees, and a prepayment penalty. Request a dated payoff statement from the lender or servicer before sending the final payment.
Sources and further reading
Informational only; not financial advice. Figures reviewed September 2026.