Four debts total $38,500. Their minimums add to $1,010, and the household commits another $490, so both snowball and avalanche receive the same $1,500 monthly budget. The avalanche costs $5,044 in modeled interest; the snowball costs $5,179. Adding $250 per month reduces the avalanche result to 2 yr 1 mo and $4,105.
This is a fair strategy comparison because starting balances, APRs, first payment month, and total payment budget are identical. Only the order receiving extra money changes. Comparing a $1,500 avalanche with a $1,700 snowball would measure budget as well as order and could not answer which ordering rule caused the difference.
Scenario at a glance
- Starting debt
- $38,500
- Four balances
- Equal monthly budget
- $1,500
- Minimums plus rollover money
- Avalanche result
- 2 yr 6 mo
- $5,044 total interest
- Snowball result
- 2 yr 6 mo
- $5,179 total interest
The four-debt starting point
The balances deliberately create a real tradeoff. The store card is smallest, but the larger credit card has the highest APR. Snowball therefore creates an earlier small-balance win, while avalanche directs the extra payment toward the most expensive rate first. Installment loans follow later as higher-priority debts close.
| Debt | Starting balance | APR | Minimum payment |
|---|---|---|---|
| Store card | $2,400 | 18.9% | $80 |
| Credit card | $7,600 | 24.5% | $230 |
| Personal loan | $11,500 | 11.2% | $310 |
| Auto loan | $17,000 | 6.4% | $390 |
Worked example
Hold the budget constant and change only the order
Add starting balances
$2,400 + $7,600 + $11,500 + $17,000 = $38,500
Both simulations begin with exactly this principal.
Build the monthly debt budget
$1,010 minimums + $490 extra = $1,500
The same amount is available to snowball and avalanche every month.
Set the snowball order
Store card → Credit card → Personal loan → Auto loan
Extra cash follows smallest current balance first, then rolls forward.
Set the avalanche order
Credit card → Store card → Personal loan → Auto loan
Extra cash follows highest APR first, with the calculator resolving the complete monthly schedule.
Compare completed schedules
$5,179 − $5,044 = $134 interest difference
This is the mathematical cost of the ordering choice under the shared assumptions.
Debt balance over time
| Position | Snowball debt | Snowball payoff | Avalanche debt | Avalanche payoff |
|---|---|---|---|---|
| 1 | Store card | 2027-01 | Credit card | 2027-09 |
| 2 | Credit card | 2027-11 | Store card | 2027-11 |
| 3 | Personal loan | 2028-07 | Personal loan | 2028-07 |
| 4 | Auto loan | 2029-02 | Auto loan | 2029-02 |
How payment rollover works
Every active debt receives at least its minimum. The strategy payment goes to the current target. When that target closes, its former payment capacity is not spent elsewhere; it becomes available to the next debt. That is the mechanism behind both methods, despite their different ordering rules.
The rollover sequence
In a payoff month, the target may need less than the full budget. The calculator immediately applies remaining capacity according to the strategy instead of losing it. This is why simply adding minimum-payment payoff dates cannot reproduce a rollover schedule.
Time and interest comparison
Strategy and extra-payment outcomes
| Plan | Monthly budget | Payoff time | Total interest | Interest versus baseline avalanche |
|---|---|---|---|---|
| Snowball | $1,500 | 2 yr 6 mo | $5,179 | $134 |
| Avalanche | $1,500 | 2 yr 6 mo | $5,044 | $0 |
| Avalanche + $250 | $1,750 | 2 yr 1 mo | $4,105 | -$940 |
Cumulative interest at payoff
What the additional $250 changes
Increasing the monthly budget from $1,500 to $1,750 saves 5 months and $940 of modeled interest. The effect is larger than simply multiplying $250 by the time saved because earlier principal reduction also prevents later interest.
The extra-payment result is a third scenario, not evidence that the original comparison was unfair. Snowball and avalanche remain compared at $1,500. The $1,750 case separately answers what a budget change can do.
Use the closing dates as operational checkpoints
The final debt-free month is important, but the individual closing months are more actionable. When the first debt reaches zero, the household should confirm the lender’s final amount, stop any obsolete autopay only after the account is settled, and direct the planned rollover to the next target. A payoff schedule fails if the released payment quietly returns to spending.
Small last payments also explain why a month’s total can be below the usual $1,500. The calculator caps payment at the remaining debt and rolls available capacity forward where possible. On the final month, no next debt remains, so the household may pay less than the regular budget. That is a schedule detail, not a change in commitment.
If a new charge appears, the comparison should be rerun from updated balances. Continuing to quote the old interest total would create false precision. The same applies when an APR changes or a minimum payment formula resets. The most useful schedule is a current decision tool, not a promise that the original inputs will remain unchanged for years.
Limits and actions to test
The calculator assumes no new borrowing, fixed APRs, and a stable monthly budget. It does not model promotional expirations, penalty rates, skipped payments, taxes, or creditor-specific payment allocation. For the conceptual tradeoffs between methods, read the debt payoff fundamentals guide.
- Enter statement balances, APRs, and true minimum payments for every debt.
- Set one total amount you can repeat and compare both strategies without changing it.
- Review each debt’s closing month, not only the final debt-free date.
- Test a modest extra amount and confirm it leaves room for required expenses.
- Recalculate after a rate change, new charge, balance transfer, or payment interruption.