Quick answer
A debt payoff calculator combines all your debts into one plan with a payoff date. With $15,400 spread across two cards and a loan, paying $700 a month using the avalanche method makes you debt-free in 27 months with $3,089 of interest. Paying only the minimums ($370 a month) takes 73 months and $11,438 of interest — the same debts, at nearly four times the interest cost.
How the Debt Payoff Calculator works, step by step
Add each debt as a row: balance, APR and minimum payment. Set the total monthly amount you can commit. The calculator pays every minimum, directs the surplus at one target debt at a time (highest APR under avalanche, smallest balance under snowball), and rolls freed payments into the next target as debts clear.
The output that matters is the debt-free date and the total interest under your chosen budget, shown for both methods side by side. Then change the budget by $50 either way and watch the date move — the relationship is steep, because extra payments cut principal, which cuts next month's interest, which frees more principal. Small permanent increases beat occasional heroic ones.
In the example the two methods agree exactly, which happens whenever the highest-rate debt is also the smallest balance: the 29.99% store card ($2,100) is targeted first under both, clearing in month 6, followed by the 24.99% credit card in month 18 and the 11.5% personal loan in month 27. When the methods diverge, the calculator shows the interest difference so you can price the motivation snowball buys.
Two disciplines make the plan real. Stop adding to the balances — a payoff plan run alongside new card spending is a treadmill. And keep a starter emergency fund, even $1,000, so the first surprise does not go back on a card at 25%. The plan also warns you if any debt's minimum does not cover its monthly interest, in which case that debt never clears on minimums alone.
Watch the minimums-only comparison, because it is the cost of doing nothing extra. The example's $370 of minimums takes 73 months and $11,438 of interest — $8,350 more than the $700 plan. The extra $330 a month does not just buy speed; it buys back almost four years of payment-free life and a credit profile with no revolving balances in it.
The formula
Simulated month by month across all debts: interest = balance × APR ÷ 12 per debt; minimums paid first; surplus to the target debt (highest APR under avalanche, smallest balance under snowball), rolling freed minimums forward as debts clear. Debt-free date = first month all balances reach zero; total cost = sum of all interest.
Worked example — try it on the calculator above
Worked example: $15,400 across three debts, $700 a month
Credit card: $5,800 at 24.99%, minimum $145. Store card: $2,100 at 29.99%, minimum $60. Personal loan: $7,500 at 11.5%, minimum $165. Minimums total $370; the plan commits $700, so $330 attacks the 29.99% store card first. Result: debt-free in 27 months, total interest $3,089, with the store card gone in month 6 and the credit card in month 18. Pay minimums only and the same debts take 73 months and $11,438 of interest. The extra $330 a month saves $8,350 and returns three years and ten months of payment-free life.
Frequently Asked Questions
Avalanche or snowball — which should I pick here?
Avalanche (highest APR first) is always the cheapest; the calculator shows the exact interest difference for your debts. In the worked example the gap between methods is zero, because the highest-rate debt is also the smallest. If the difference is under about $300 and an early cleared account would keep you motivated, snowball is a reasonable purchase. If the gap is in the thousands, take the avalanche.
How much should my monthly payoff budget be?
Start from your budget's real surplus: income minus essential spending and minimum payments. Commit an amount you can sustain in a bad month, not your best month — plans fail by abandonment, not by arithmetic. A useful floor: your minimums plus at least 10% of the total balance's monthly interest bill redirected to principal.
Should I use savings to pay off debt in one go?
Above a basic emergency buffer, usually yes for high-APR debt: savings earning 4% cannot compete with a card charging 25%. Keep one month of essentials in cash, direct the rest at the highest-rate balance, and rebuild savings once the debt is gone — the freed payments rebuild it faster than you expect.
Does a debt payoff plan affect my credit score?
Positively, in most cases. Paying down revolving balances lowers utilisation, a major scoring factor, and a run of on-time payments builds history. The score dips to avoid come from closing old cards (keep no-fee cards open), missing a minimum while focusing elsewhere (never do this — the plan pays every minimum), and new hard inquiries from consolidation loans.
Estimates, not advice. This calculator provides educational estimates based on the inputs you enter and the assumptions shown on this page. It is not financial, tax or investment advice, and it cannot see your full situation. Verify important figures against official sources, and consider a qualified professional for decisions about your own money. See our Disclaimer and Methodology.