Debt Payoff Calculator

Interest is charged on the outstanding balance. Whatever you pay above the interest due goes to principal, and principal removed today never generates interest again — not next month, and not in any month for the rest of the term. That is why the effect compounds. An extra amount lowers the balance, which lowers next month's interest charge, which means a larger share of your *ordinary* payment reaches principal too, which lowers the balance faster still. The saving is not the extra payment; it is the extra payment plus every interest charge it cancelled downstream. The leverage scales with the rate. On low-rate debt the effect is real but modest. On high-rate revolving debt it is dramatic — the interest being cancelled is large, so a moderate monthly addition can remove years from the schedule. Adjust the extra field by small amounts and watch the months-saved figure move disproportionately; that non-linearity is the whole point of the page.

This is the most common way a good plan quietly fails, and it is administrative rather than mathematical. Send a servicer more than the amount due and it may not reduce your balance. Some apply the surplus as a prepaid future installment, advancing your due date instead — the account shows "paid ahead", the balance is unchanged, and interest keeps accruing exactly as before. Others hold funds in a suspense account until they add up to a full payment. So state the instruction explicitly: extra funds are to be applied to principal, not to a future payment. Many servicers offer this as a setting or a separate payment type online; if not, send it in writing, and then verify on the next statement that the principal balance dropped by what you sent. Two other checks before making a large payment. Confirm whether the loan carries a prepayment penalty — whether one applies, and for how long, depends on the loan type and the contract. And on a mortgage, confirm the money is not diverted into an escrow account for taxes and insurance, which is not the same as reducing the loan.

With more than one debt, the extra amount should go to one debt at a time rather than being spread evenly. Spreading it thinly is the only approach that is clearly worse than both alternatives, because it delays every payoff without accelerating any. The avalanche method targets the highest APR first, then rolls that freed-up payment onto the next-highest, and so on. This is the arithmetically optimal order: it always produces the least total interest and, for a given monthly outlay, the earliest overall debt-free date. If the goal is to minimize money paid, this is the answer, and there is no rate at which it is not. The snowball method targets the smallest balance first regardless of rate, clearing individual accounts quickly. It costs more in interest whenever the small balances are not also the high-rate ones. Its argument is behavioural: closing an account is a visible, discrete completion, and the method's advocates hold that people are more likely to stay with a plan that produces those. That is a claim about follow-through, not about math. The honest framing is that avalanche wins on cost, snowball on momentum, and a plan you abandon in month four saves nothing. Which trade-off suits you is a self-assessment this page cannot make.

One rule survives regardless of which method you choose: paying extra on cheap debt while carrying expensive debt costs you money, and the size of the mistake is the difference in rates. Carrying a balance at a revolving-credit rate while overpaying a low-rate installment loan is the clearest example. The extra dollars are cancelling small future interest charges instead of large ones, and the gap accumulates every month the arrangement continues. A few structural details change the picture and are worth checking before ordering your debts. Some debt carries tax treatment that affects its effective cost; whether any deduction applies to you depends on your circumstances and is a question for IRS guidance or a tax professional, not a rule of thumb. Some loans have flexible or income-based repayment terms or forgiveness features that make aggressive prepayment less obviously correct. And secured debt — where a missed payment risks a car or a home — may deserve priority for reasons that have nothing to do with its rate. Where terms vary by lender or plan, the loan agreement or plan document is the authority.

The model is deliberately simple, and each simplification pushes in a predictable direction. It assumes a fixed APR for the whole payoff. Many credit cards and some loans carry variable rates tied to an index, so the real schedule shifts when the rate does. It assumes no new borrowing — a single new charge on a card being paid off changes the entire projection. It assumes every payment arrives on time, with no late fees or penalty charges, and it ignores fees generally. It also treats the extra payment as a constant every month. In practice, one-off amounts — a tax refund, a bonus — behave the same way and often better, since a lump sum early cancels more interest than the same money spread over a year. Finally, a note on order of operations. Directing every spare dollar at debt while holding no cash buffer at all means the next unexpected expense goes back on the card, undoing the progress at the same high rate. Many budgeting frameworks suggest a small starter emergency fund alongside, rather than after, aggressive repayment. If the payments have become unmanageable, nonprofit credit counseling is a documented route and the CFPB publishes guidance on choosing a legitimate provider.