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Snowball vs Avalanche: How to Calculate the Cost of Each Debt Payoff Method
Avalanche costs less. Snowball finishes accounts sooner. Before choosing on principle, calculate the gap for your own debts — sometimes it is hundreds, sometimes it is a rounding error.
Both methods pay the minimum on every debt and put all spare money against one target debt, then roll that payment onto the next when it clears. The only difference is the order. Avalanche targets the highest interest rate first and costs the least. Snowball targets the smallest balance first and clears individual accounts sooner.
The comparison formula
Interest cost difference = Total interest in Plan A − Total interest in Plan B Payoff-method savings = absolute difference between the two modeled total-interest amounts. Keep the total monthly payment, starting balances, rates and fees the same when comparing methods.
Setting up the calculation
List every debt with three columns: balance, interest rate, and minimum payment. Then work out your total monthly debt payment — the sum of the minimums plus whatever extra you can add.
That extra amount is the whole engine of both methods. Without it, you are just making minimum payments and the ordering makes no difference at all.
Order the list by rate, highest first, for avalanche. Order it by balance, smallest first, for snowball. Everything else about the two is identical.
A worked comparison
Assume 250 a month extra, so 669 in total.
Avalanche order: store card (27.9%), card A (24.9%), card B (19.9%), car loan (7.5%).
Snowball order: store card (600), card A (1,200), card B (4,500), car loan (7,800).
In this case the first two are the same under both methods, because the smallest balance also happens to carry the highest rate. The orders diverge only at step three, and they converge again at the end. Running both through a repayment schedule gives roughly 25 months either way, with avalanche saving around 90 in total interest.
| Debt | Balance | Rate | Minimum |
|---|---|---|---|
| Credit card A | 1,200 | 24.9% | 36 |
| Credit card B | 4,500 | 19.9% | 113 |
| Car loan | 7,800 | 7.5% | 245 |
| Store card | 600 | 27.9% | 25 |
| Total | 14,100 | 419 |
When the gap is large and when it is not
That last point is not a hedge. A plan that gets abandoned in month four costs more than either method, so the honest comparison is between avalanche completed and snowball completed — and if the psychological difference is what determines completion, it belongs in the decision.
- The gap is small when your debts have similar rates, or when the highest-rate debt also happens to be the smallest.
- The gap is large when a big balance carries a much higher rate than a small one — for example a 9,000 card at 25% alongside a 700 loan at 4%.
- The gap grows with the total amount owed and with how long repayment will take.
- The gap shrinks the more extra you can put in each month, because the whole schedule compresses.
- If the difference comes out under a few hundred over the full term, treat it as a tie and pick whichever you will actually finish.
How to calculate it yourself
A spreadsheet handles this in one column per debt and one row per month. The step people skip is the fifth: rolling the freed-up payment forward is what makes either method work, and quietly reabsorbing it into ordinary spending turns a 25-month plan into a much longer one.
- List every debt with balance, annual rate and minimum payment.
- Convert each annual rate to monthly by dividing by 12.
- Each month, add interest to each balance (balance x monthly rate), then subtract that debt's payment.
- Send the minimum to every debt except the target, and everything left to the target.
- When a debt reaches zero, add its full previous payment to the next target rather than absorbing it back into general spending.
- Track cumulative interest paid, then repeat the whole exercise with the other ordering and compare the two totals.
Traps when comparing payoff methods
- Choosing a method before running the numbers. The difference between them varies enormously depending on the specific mix of balances and rates.
- Ignoring promotional rates that expire. A 0% balance that reverts to 22% in four months should be treated at the rate it will carry, not the rate it carries now.
- Adding new debt during repayment, which resets the plan without it being obvious.
- Leaving no buffer at all, so the first unexpected expense goes back onto a card.
- Comparing methods on time-to-clear alone. Both finish at a similar time in most cases; the real difference is total interest paid.
- Forgetting fees. An annual card fee or a loan early-settlement charge changes the effective cost of clearing that debt.
A note on consolidation
Consolidating several debts into one lower-rate loan is a third option, and it interacts with both methods. The calculation to run is total interest under your current plan versus total interest on the consolidation loan, including any arrangement fee, over the same period.
Two things make consolidation look better than it is. A longer term reduces the monthly payment while increasing total interest paid, which is easy to miss when the comparison is framed as a monthly figure. And freeing up credit lines often leads to those lines being used again, which restores the original problem alongside the new loan.
Compare total cost over the full term, not the monthly payment.
Assumptions and limitations
Both calculations assume rates stay fixed and that you make every payment on schedule. Variable rates, a missed payment penalty, or a promotional period ending all change the outcome, and penalty rates in particular can be far above the standard rate.
They assume the extra payment stays constant. In reality it fluctuates, so treat the projected payoff date as a planning estimate rather than a commitment, and rerun the schedule after any month that differs materially.
They also ignore everything outside the debts themselves. If clearing debt aggressively means having no accessible savings, the plan is fragile in a way the arithmetic does not show — which is the argument for keeping a small buffer even while the interest cost says otherwise.
Compare payoff methods using the same assumptions
A fair snowball-versus-avalanche comparison keeps the total monthly payment available for debt reduction constant. Only the order in which extra money is directed should change. Include each balance's interest rate, minimum payment and current balance, then compare the modeled payoff date and total interest. If one method appears cheaper only because it assumes a larger payment, the comparison is not measuring the methods themselves.
Frequently asked questions
Which method is mathematically better?
Avalanche, always, because paying the highest rate first minimises total interest. The question is whether the saving is large enough to matter in your specific case.
Should I pay minimums on everything else?
Yes. Missing a minimum triggers fees and often a penalty rate, which costs more than any ordering decision would save.
Does the order matter if all my rates are similar?
Barely. When rates are within a couple of points of each other, the interest difference is usually small, and picking by balance is a reasonable choice.
What about a debt with no interest at all?
Under avalanche it goes last, since it costs nothing to carry. Keep paying its required minimum, and check whether the zero rate expires — interest-free periods that revert to a standard rate need to be cleared before the deadline.
Do both methods require paying every minimum payment?
Yes. In a typical comparison, minimum payments are made on all debts and any additional amount is directed according to the chosen strategy.
Why can the snowball method cost more interest?
It prioritizes the smallest balance rather than the highest rate. That can produce quicker account closures but may leave a higher-rate balance outstanding longer.
Conclusion
Run both orderings through a simple month-by-month schedule using your real balances and rates before deciding. If avalanche saves a meaningful amount, take it. If the gap is trivial, choose the one you are most likely to finish. Either way, the two things that determine the outcome are how much extra you can put in and whether you roll each cleared payment forward, and both of those matter far more than which ordering you picked.
Figures in this article are illustrative. Results depend on your own rates, fees, taxes and circumstances, and are for educational and planning purposes rather than financial advice.