Snowball vs. avalanche: 12 reproducible comparisons
By Xavier Carraté · Editor & Researcher
How much does payment order change the cost? We designed four debt portfolios and applied three extra-payment amounts to each. Within each comparison, snowball and avalanche receive the same budget.
Synthetic data. No row represents a person, survey response or available loan. These 12 selected comparisons explain mechanisms; they do not estimate your savings or the percentage of people who will finish a plan.
| Portfolio / debt | Balance | Nominal annual rate | Fixed monthly payment |
|---|---|---|---|
| One debt: ordering has no effect · A | $5,000.00 | 22% | $200.00 |
| Smaller debt has the lower rate · A | $1,000.00 | 8% | $35.00 |
| Smaller debt has the lower rate · B | $9,000.00 | 24% | $225.00 |
| Smaller debt has the higher rate · A | $1,000.00 | 24% | $35.00 |
| Smaller debt has the higher rate · B | $9,000.00 | 8% | $225.00 |
| Two debts with equal rates · A | $1,000.00 | 18% | $35.00 |
| Two debts with equal rates · B | $9,000.00 | 18% | $225.00 |
| Portfolio | Monthly extra | Total budget | Snowball months | Avalanche months | Snowball interest | Avalanche interest | Interest difference: snowball − avalanche |
|---|---|---|---|---|---|---|---|
| One debt: ordering has no effect | $0.00 | $200.00 | 34 | 34 | $1,749.90 | $1,749.90 | $0.00 |
| One debt: ordering has no effect | $100.00 | $300.00 | 21 | 21 | $1,021.61 | $1,021.61 | $0.00 |
| One debt: ordering has no effect | $250.00 | $450.00 | 13 | 13 | $643.18 | $643.18 | $0.00 |
| Smaller debt has the lower rate | $0.00 | $260.00 | 72 | 72 | $8,478.18 | $8,478.18 | $0.00 |
| Smaller debt has the lower rate | $100.00 | $360.00 | 41 | 40 | $4,619.59 | $4,333.25 | $286.34 |
| Smaller debt has the lower rate | $250.00 | $510.00 | 26 | 25 | $2,772.09 | $2,533.09 | $239.00 |
| Smaller debt has the higher rate | $0.00 | $260.00 | 47 | 47 | $1,998.81 | $1,998.81 | $0.00 |
| Smaller debt has the higher rate | $100.00 | $360.00 | 32 | 32 | $1,170.59 | $1,170.59 | $0.00 |
| Smaller debt has the higher rate | $250.00 | $510.00 | 22 | 22 | $789.01 | $789.01 | $0.00 |
| Two debts with equal rates | $0.00 | $260.00 | 58 | 58 | $5,021.99 | $5,021.99 | $0.00 |
| Two debts with equal rates | $100.00 | $360.00 | 37 | 37 | $3,033.11 | $3,033.11 | $0.00 |
| Two debts with equal rates | $250.00 | $510.00 | 24 | 24 | $1,931.96 | $1,931.96 | $0.00 |
What these examples show
- With one debt there is no order to change, so both methods give the same result.
- When the smaller debt has the higher rate, both methods prioritize the same account in our two-debt portfolio.
- When the smaller debt has the lower rate, adding $100 creates a choice about where the extra goes. In that row, the interest difference is $286.34 and the duration difference is 1 month. Those are row-specific results, not average savings.
- Comparing different extra amounts also changes the total budget. That change does not isolate the payment method: it requires more money each month.
Every row here pays off within the model horizon; that is a property of our selected inputs. The model does not observe consistency, stress, income changes or dropout. A calculated cost advantage does not establish which method you can sustain.
Method and limits
Four portfolios × three extra payments × two methods produce 24 schedules and 12 paired comparisons. There is no random sampling or population weighting. Results are not averaged as though this were a representative sample.
Each month, interest is charged to each account’s opening balance using its nominal annual rate divided by 12, rounded half up to cents. Entered fixed payments are covered first; the remainder, including freed payments, goes toward the priority debt that same month. Snowball prioritizes the smallest opening balance; avalanche prioritizes the highest rate. Ties are resolved by rate or balance, then original input order. The final payment is capped by the amount owed.
USD, fixed rates, no new purchases, fees, late payments, taxes or reinvestment. The computation stops at 1200 months; any remaining balance or stop status is retained in the downloads, without labeling an unpaid debt paid off. Actual interest may accrue daily, and the creditor determines required payments.
The CFPB reducing-debt worksheet describes balance-first and interest-first approaches. The CFPB has not reviewed or endorsed these simulations.
Download and reproduce
- CSV summary of all 24 results
- JSON with every schedule
- Exact input data
- Reproduction script (Node.js)
- Unmodified debt model used
To reproduce: save the script, input data and debt model in one folder, keeping their filenames. With Node.js installed, run node debt-payoff-study-reproduce.cjs > reproduced.json. The output should match the downloadable JSON byte for byte. No additional packages or network connection are needed during calculation.
Prepared: 2026-09-07. Model version: 2026-09-06.1. Identifier: synthetic-debt-payoff-v1.
You can share this study’s link and cite “GetDebtFree.tools, synthetic debt payoff comparisons, version synthetic-debt-payoff-v1.” Preserve the assumptions and the distinction between simulations and observed data when reusing results.
Try your own figures
Use the debt payoff planner with a sustainable budget. Before increasing payments, review bills and pay dates. To compare payoff with investing, use the same-budget, same-horizon comparison.