➕ Loan Payoff Calculator With Extra Payments

On a $15,000 personal loan at 9% APR with a standard 60-month term, the required monthly payment is approximately $311. Adding $100 per month — paying $411 total — reduces the payoff from 60 months to roughly 44 months and saves approximately $787 in interest. The savings compound because each early principal reduction lowers the base on which next month's interest is calculated. On a larger loan — $30,000 at the same rate — the same extra $100/month saves closer to $1,400 and cuts nearly 18 months off the timeline. Run your specific balance and rate in the calculator above to see your exact savings.

For installment loans, interest is calculated on the current outstanding balance before each payment is applied — meaning the interest portion is subtracted first, and whatever remains reduces principal. On a $15,000 loan at 9% APR, the first payment carries roughly $112 in interest; an extra payment beyond the required amount removes future interest on the principal it eliminates. Credit cards work differently — an extra payment reduces the revolving balance immediately and next month's interest is calculated on the lower balance. Both work in your favor; the mechanism just differs between loan types.

Yes — most lenders apply extra payments to your next scheduled payment, covering future interest first, rather than directly to principal unless you explicitly designate otherwise. To ensure your extra payment reduces the principal balance: write "apply to principal" in the memo field of a check, select the principal-only option in your lender's online portal, or contact customer service to confirm their process. Some lenders — particularly for mortgages and student loans — require a separate transaction or written instruction. Without that direction, what you intend as a principal reduction may simply advance your next due date rather than shortening your loan term.

Monthly extra payments almost always outperform an equivalent lump sum paid later, because each monthly reduction lowers the balance on which interest accrues during the months you would have been saving. Paying an extra $100 per month for 12 months saves more in interest than a single $1,200 payment at month 12, because the earlier months of reduced balance generate earlier interest savings. The lump sum approach makes practical sense only when you're building toward a specific milestone — paying off a balance completely, or reaching a threshold that triggers a rate reduction — where the structural benefit outweighs the timing advantage of monthly payments.

Mechanically, yes — extra principal payments on student loans reduce the balance and lower total interest, the same as any installment debt. However, if you're enrolled in an income-driven repayment plan or pursuing Public Service Loan Forgiveness, extra payments may not benefit you financially and could cost you money. Under income-driven plans, payments are based on discretionary income regardless of balance, and remaining balances can be forgiven after 20–25 years. In those programs, aggressively paying down principal shortens the timeline to zero but eliminates the forgiveness benefit you've been building toward. Confirm your repayment plan type before making extra principal payments on federal loans.

This is a math question with a clear answer: if your loan APR exceeds your savings account yield, pay down the loan — it's a guaranteed return. At current rates, high-yield savings accounts are offering approximately 4.5–5.0% APY, which means paying extra on a personal loan at 9–12% APR almost always wins — the guaranteed return of debt elimination beats a 4.75% yield on cash. The math flips for low-rate debt: if you have a 3.5% auto loan from 2021, there's a strong case for keeping money in a high-yield account earning more than your loan rate. Your loan APR is the benchmark — compare it directly to your best available yield.

On a $20,000 auto loan at 7% APR with a 60-month term, adding $200 per month to the standard $396 payment cuts the payoff from 60 months to approximately 41 months — saving 19 months and roughly $1,200 in interest. On a $25,000 personal loan at 10% APR over 60 months, the same $200 extra saves 18 months and approximately $2,100. The month savings scale with loan size and rate: the higher the rate and the larger the balance, the more work each extra dollar does. Use the calculator above with your specific balance, rate, and term to see your exact month and interest savings.