Debt Payoff Calculator

Juggling several debts and wondering whether to attack the smallest balance or the highest rate first? This free debt payoff calculator compares the debt snowball and avalanche methods side by side on your real numbers — up to five debts. Enter each balance, APR, and minimum payment, add any extra monthly payment, and see the exact payoff order, months to debt-free, and total interest for both strategies.

How to Use the Debt Payoff Calculator

Five steps to your side-by-side payoff plan:

1. List up to five debts. For each one, enter a name (card, loan, medical bill — whatever helps you recognize it), the current balance, the annual APR, and the minimum monthly payment. The page comes pre-filled with three sample debts so you can see how it works instantly — replace them with your real numbers.
2. Set your extra monthly payment. This is the amount on top of all your minimums that you can throw at debt each month. It applies to both methods so the comparison stays fair.
3. Press Calculate Payoff Plan. The calculator runs a real month-by-month simulation for each method — accruing interest, applying minimums, then directing your extra payment and any freed-up minimums at the current target debt.
4. Read the two columns. Each shows the payoff order, total months until you are debt-free, and total interest paid. The verdict line at the bottom tells you exactly how many dollars and months the avalanche saves versus the snowball.
5. Experiment. Try $0 extra versus $100, $200, or $500. Watch how a bigger extra payment collapses the total interest — that number is the most honest argument for cutting spending and redirecting it at debt.

Leave debts 4 and 5 blank if you have fewer than four debts — only the debts you fill in are counted.

The Two Methods Explained

Both methods pay the minimum on every debt each month and send all extra money to one target debt. The only difference is which debt gets targeted first — and when a debt dies, its minimum payment is freed up and added to the attack on the next target. That rolling payment is what makes both methods accelerate.

The snowball method targets debts from the smallest balance to the largest, ignoring interest rates. It is the psychological play: your smallest debt disappears fast, and that early win gives you momentum to keep going. Behavioral researchers have found people are more likely to stick with debt payoff when they see early progress, even if the math is not perfect.

The avalanche method targets debts from the highest APR to the lowest, ignoring balances. It is the math-optimal play: every dollar of extra payment kills the most expensive interest first, so total interest paid is always the lowest possible (or tied with the snowball). If you are motivated by saving money rather than by quick wins, the avalanche is your method.

Both methods share the same core formulas. Monthly interest on each debt is calculated as:

Payoff order rules: snowball sorts debts by balance ascending (lowest first); avalanche sorts debts by APR descending (highest first). Ties keep their original entry order. Each month, every unpaid debt accrues its monthly interest, then receives at least its minimum payment (or the remaining balance if smaller), and finally the extra payment plus the freed minimums from already-paid debts are applied to the first unpaid debt in the order.

One trap to watch for: if a debt's minimum payment is smaller than its monthly interest charge, the balance grows instead of shrinking — the debt can never be paid off. The calculator flags this explicitly, because it means you need to raise the payment or lower the rate before any strategy can work.

Worked Example

Let us run the pre-filled sample: a $1,200 store card at 24.99% APR ($35 minimum), a $4,500 Visa at 18.99% APR ($95 minimum), and a $9,800 car loan at 7.49% APR ($210 minimum), with $150 extra per month. These numbers were run through the calculator's actual simulation, so every figure below is the real computed result:

Notice something interesting: snowball and avalanche produce identical results here — the same payoff order, 38 months, and $2,743.68 interest. That is not a bug. The smallest balance (Store Card) also has the highest APR, so both sorting rules pick the same target at every step. The methods only diverge when the highest-rate debt is not the smallest balance — for example, a $3,000 card at 12% versus a $6,000 card at 24% sends the two methods down different paths. The big lesson is in step 11: $150 extra a month saves $3,350 and more than two years.

Limitations

This calculator is a planning tool, not a crystal ball. It assumes every debt has a fixed APR — variable-rate credit lines and adjustable loans can change your interest charge month to month. It does not model balance-transfer offers, promotional 0% periods that expire, penalty APRs after a late payment, annual fees, or late fees, all of which move the real payoff date. It also assumes you stop spending on the accounts: new purchases are the most common reason real payoffs take longer than planned.

Minimum payments are treated as fixed dollar amounts; many cards calculate minimums as a percentage of the balance, which declines as you pay down — our fixed-minimum model is slightly conservative in that case. The calculator does not model credit-score effects (paying off revolving debt usually lowers your utilization and helps your score, but closing your oldest card can shorten your credit history), tax implications, or consolidation/refinancing options. These are estimates for planning only — not financial advice. For large or complicated debt, talk to a nonprofit credit counselor or a financial professional.

A mortgage is a debt payoff plan on a longer clock, and the tactics transfer: our guide to extra mortgage payments shows how small overpayments reshape the interest total.

Money freed from interest has to go somewhere deliberate. One of the quietest leaks is the weekly shop, and our unit price guide shows how comparing cost per ounce or per sheet — not the sticker — puts real dollars back into the payoff plan every single week.

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