Avalanche versus snowball, in one sentence each
Both strategies start from the same rule: pay the minimum on every debt, then put whatever extra you can find toward exactly one of them. They only disagree about which one. The avalanche method sends the extra to whichever debt carries the highest interest rate, whatever its balance. The snowball method sends it to whichever debt has the smallest balance left, whatever its rate. Once that target debt is gone, its minimum payment does not disappear from your budget, it rolls onto the next debt in the same order, on top of the extra amount that was already going there. That rolling-over is the mechanic doing the actual work in both strategies, and it is why the gap between them opens up gradually rather than all at once.
Mathematically, avalanche wins or ties every time, because it always puts extra money against whichever balance is generating the most interest, the fastest way to shrink the total interest bill over the whole plan. Snowball is not a mathematical rule at all, it is a behavioural one: clearing a small debt outright, quickly, gives many people a visible win early on, and that win is what keeps them making the extra payment at all in month four or month fourteen. Neither framing is wrong. Ramsey Solutions, which popularised the snowball method, is explicit that it trades a little interest for motivation; Experian's comparison of the two reaches the same conclusion from the other side, that avalanche is cheaper on paper while snowball is often the one people actually stick with. This calculator runs both against your own numbers so you can see exactly how big that trade-off is for you, rather than taking either argument on faith.
How the simulation actually runs
There is no single formula for a multi-debt rollover, because which debt is being paid down fastest changes every time one clears, so this calculator simulates it month by month instead, the same discipline the Amortization Calculator uses for a single loan. Every month, interest accrues on whatever each debt still owes; every debt's own minimum is paid, or whatever is left of its balance if that is less; then the extra amount, plus the minimum of any debt already paid off, is sent to the current target debt in the strategy's order, clearing it and moving to the next one in the same month if money is left over. Which debt is "first" is worked out once at the start from your opening balances and rates. It never needs recalculating, because a debt that starts with the highest rate keeps that rate until it is paid off, and the same is true of the smallest balance relative to the debts still open around it.
Every debt keeps being paid its own minimum for as long as it is open, whichever strategy is running; the only thing that ever moves between avalanche and snowball is where the spare money above those minimums goes. That is worth repeating because it is the detail that is easy to misread from the results: neither method risks a debt going unpaid while another gets attacked, both keep every minimum ticking over throughout.
The rollover, and why it accelerates
The rollover is what turns a fixed monthly budget into a shrinking payoff time. All the minimums plus the extra amount add up to the actual monthly budget in both strategies, and that total never grows on its own. What changes is how much of it lands on a single balance at once. Early on, only the extra amount is concentrated on the target debt. Once that debt clears, its minimum joins the extra amount, so a bigger sum now attacks the next debt, clearing it faster than the first one took, which frees an even larger sum for the one after. That is the "snowball" the informal name refers to: the amount attacking whatever is left keeps growing as each debt in front of it disappears, whichever order you chose to attack them in.
What paying only the minimums actually costs
The "minimums only" row further up runs a third scenario with no strategy behind it at all: every debt paid on its own fixed minimum, nothing extra, and nothing rolled over once one clears. Whatever budget that debt's minimum used to need simply is not paid to anyone else; it is treated as spent elsewhere rather than redirected. That is the realistic default for anyone who has not deliberately chosen a payoff strategy, and it usually takes years longer and costs a great deal more in interest than either avalanche or snowball on the same debts, because none of the acceleration described above ever happens.
There is a sharper trap hiding inside that baseline. A minimum payment only reduces a balance if it is larger than the interest that balance generates that month; multiply the balance by the monthly rate, the APR divided by twelve, to get that floor. A minimum at or below the floor makes no progress at all, the balance holds steady or grows even while payments are being made, the same guard the Payment Calculator applies to a loan payment that can never clear the balance it is meant to be repaying. This calculator checks every debt against its own floor and flags any that fail the test; avalanche and snowball still clear a flagged debt eventually, since the rollover sends it real extra money once it becomes the current target, but it makes zero progress in the minimums-only row.
Choosing your inputs
Balance and minimum payment are whatever your latest statement says; APR should be the annual rate actually charged, not an advertised or promotional rate that has since expired. A card with no current balance is not worth listing at all. The extra amount is the one figure genuinely worth experimenting with: try it at what you can manage today, then try it a little higher, since the acceleration effect described above means even a modest increase tends to buy back more time than it costs in extra outlay, particularly on higher-rate debts near the top of the avalanche order.
If a single high-rate debt is large enough that spreading payments across several accounts feels unwieldy, rolling everything into one loan at a lower blended rate is a different approach entirely, worth comparing against either payoff order here rather than assumed to be automatically better. The Personal Loan Calculator works out whether a consolidation loan's rate and fees actually beat what you are paying across these separate debts today.
Reading the results
The headline names whichever strategy comes out cheaper on your own numbers and by how much; when the two are close enough to call it even, the calculator says so honestly rather than manufacturing a winner. The chart plots the combined balance still owed, month by month, as two lines, one per strategy; where they visibly separate is where one order's rollover has started concentrating money faster than the other's. The two payoff-order tables below it list every debt in the sequence each strategy actually tackles it, with the date it clears and the interest that specific debt cost across the whole plan, so you can see not just the total difference but which individual debts it comes from.
Questions people ask
Which method should I actually use?
Avalanche costs less overall or, at worst, ties, because it always aims extra money at the debt charging the most interest. Snowball can cost a little more but clears a debt outright sooner, which keeps some people paying the extra amount consistently when a purely mathematical plan would not. Run both against your own numbers above and weigh the interest difference against how much the early win is worth to you.
Does the order I attack debts in ever get recalculated?
No, and it does not need to be. Avalanche always ranks by APR, which does not change debt to debt over the plan; snowball always ranks by balance, and a debt that starts smallest relative to the others stays that way as all of them shrink together. The order is worked out once at the start and debts simply drop off the front of it as they clear.
Do the minimum payments on my other debts still get paid during either strategy?
Yes, every month, on every debt that still has a balance, in both strategies. The only thing that ever changes is where the money above those minimums, the extra amount plus anything freed up from a cleared debt, gets sent.
What does it mean if a debt "never clears" on minimums alone?
It means that debt's minimum payment does not exceed the interest it generates each month, so the balance cannot fall on that payment by itself, the same trap a credit card minimum can fall into. Neither the avalanche nor the snowball schedule leaves that debt stuck this way, since the rollover eventually sends it real extra money once every debt ahead of it in the order has cleared.
Why do avalanche and snowball sometimes give the same answer?
If the debt with the highest rate also happens to have the smallest balance, both strategies pick the same debt first and the schedules run identically from that point, so there is genuinely nothing to choose between them on your numbers. This calculator says so directly rather than forcing a difference that is not actually there.
Does adding zero extra still do anything useful here?
Yes. Even with no extra amount at all, the rollover still moves each debt's own minimum onto the next one in the order once it clears, which is faster than the minimums-only baseline where that freed-up money is not redirected anywhere. Add an extra amount on top to see how much further it speeds things up.
Should I consolidate these debts into one loan instead?
Sometimes, if the new loan's rate genuinely beats the blended rate you are paying across these balances today and its fees do not eat the saving. It is a separate decision from which order to pay debts in, worth comparing directly with a personal loan calculator rather than assumed either way.
This calculator gives an estimate based on the balances, rates and payments you enter, assuming interest compounds monthly and every payment is made on time and in full. Real statements vary in how interest is calculated and when it is charged; check your own agreements for the exact figures, and treat this as a planning tool rather than financial advice.