Quick answer
This calculator compares the two standard debt repayment orders on your actual debts. On a $2,400 store card at 12% and a $4,800 credit card at 28%, paid with $400 a month, the avalanche method (highest rate first) clears everything in 24 months for $1,511 of interest; the snowball (smallest balance first) takes 27 months and $2,182 — the order alone costs $671.
How the Debt Avalanche vs Snowball works, step by step
List up to three debts, each with its balance, APR and minimum payment, then enter the extra money available each month on top of all the minimums. The calculator simulates both strategies month by month on the same debts and the same budget, so the only difference between the two results is the order in which debts are attacked.
Both methods pay every minimum first. They differ only in where the leftover money goes: avalanche aims it at the highest APR; snowball aims it at the smallest balance to score an early win. When a debt clears under either method, its minimum payment rolls into the attack payment for the next debt — the roll-up that makes the payoff accelerate sharply in the later months.
Sometimes the two methods are identical, and the calculator will tell you so. If your smallest debt is also your highest-rate debt, both orders attack the same card first. That is the case with the tool's default example: the $2,200 store card is both the smallest balance and the highest APR at 29.99%, so avalanche and snowball agree exactly — 44 months and $5,621 of interest either way.
The real trade-off is the date of the first cleared debt. In the worked example, snowball clears the store card in month 9, while avalanche does not clear its first debt — the credit card — until month 18. That nine-month gap is what snowball buys you: a closed account, one fewer payment, and visible progress while the expensive debt is still being worked down.
Read the interest gap alongside the size of the debts. The gap grows with the spread between the APRs and with the size of the high-rate balance. On small balances with similar rates it is often under $100 and the choice barely matters; on a large balance at 28% against a small one at 12%, it runs to hundreds of dollars and several months — the case for avalanche strengthens as the numbers get bigger.
The formula
Both methods simulate month by month: interest = balance × APR ÷ 12 on each debt; minimums are paid first; surplus goes to the target debt (highest APR or smallest balance). Total cost = sum of all interest charged until every balance is zero.
Worked example — try it on the calculator above
Worked example: two cards, $400 a month total
Store card: $2,400 at 12% APR, $60 minimum. Credit card: $4,800 at 28% APR, $110 minimum. Minimums total $170, leaving $230 of attack money on a $400 monthly budget. Avalanche sends the $230 to the 28% card: all debt gone in 24 months, interest $1,511. Snowball sends it to the store card, clearing it in month 9 for motivation: debt-free in 27 months, interest $2,182. Same payments, same debts — the order costs $671 and three extra months, and the price of the early win is exactly $671.
Frequently Asked Questions
Is the avalanche method always cheaper?
Yes, mathematically, whenever the APR order differs from the balance order. Interest accrues fastest on the highest-rate balance, so killing it first minimises total interest. When the smallest debt is also the highest-rate one — common with store cards — both methods are identical, as the tool's default example shows.
Why do people choose snowball if it costs more?
Behaviour. Clearing a debt entirely removes a payment and produces visible progress early, and researchers have found small-debt wins can improve follow-through. A plan abandoned in month three costs more than either method. The worked example prices the trade-off precisely: here, momentum costs $671.
What if I have a 0% promotional balance?
Treat its APR as 0% until the promotion ends, then as the full go-to rate — avalanche logic handles it automatically if you update the rate at expiry. Watch for deferred-interest retail promotions, which are different: miss the deadline and interest is charged back to the purchase date.
Should I stop investing while paying off debt?
Capture any employer 401(k) match first — that is an immediate 50% to 100% return no debt can beat. Beyond the match, paying a 28% APR is a guaranteed 28% return, which no investment reliably offers. Once expensive debt is gone, redirect the entire payoff budget into investing.
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.