Debt Snowball Calculator
This page presets the snowball strategy: each month's extra money targets the smallest remaining balance first. For the full side-by-side view of all three strategies, open the Debt Payoff Planner.
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Disclaimer
Not financial advice. This calculator is for educational purposes only and is not financial advice, tax advice, or a recommendation. Consider speaking with a qualified professional about your situation.
Assumptions. Interest is calculated monthly as balance × APR ÷ 12 and applied before each payment (monthly compounding). If you leave a minimum payment blank, it is estimated as the largest of: 2% of the balance, one month's interest + 1% of the balance, or $25 — actual minimums vary by lender. Simulations stop at 600 months. Displayed amounts are rounded to the nearest cent.
Data sources. Formulas: standard amortization math. No external data feeds. Page last updated: 2026-10-18.
How the math works
The debt snowball is a payment ordering rule, not a different kind of loan math. Each month, after every debt's minimum is covered, all remaining budget is aimed at the unpaid debt with the smallest remaining balance. When that target clears, its entire payment — minimum plus the extra it was receiving — rolls into the next smallest balance the following month. The ordering is rebuilt from scratch every month, so a debt that starts large can become the target later as its balance falls below the others.
Two details of the ordering matter for the numbers. First, ties are broken by APR: equal balances target the higher rate first, which keeps the monthly sort deterministic. Second, the ordering only ever considers unpaid debts; a cleared balance drops out, and a zero-balance entry is treated as already paid. The side-by-side comparison shows what the same inputs produce under the avalanche order.
The monthly loop underneath is identical on every page of this site. Interest is applied first at balance times APR divided by 12; then minimums are paid — entered values, or an estimate of the largest of 2% of the balance, one month's interest plus 1% of the balance, or $25 when you leave the field blank; then per-debt extras; then the remainder cascades from the target down the priority order. A lump sum entered for a given month joins that cascade on the target debt first.
Because snowball aims extra money at small balances rather than high rates, its total interest at a fixed budget is never lower than the avalanche total on the same inputs; the gap is usually small when rate spreads are narrow and grows when one debt carries a much higher APR. That gap is exactly what the comparison table on the home page measures.
The hybrid strategy with the default K of 3 runs in snowball order while more than three debts remain unpaid, then finishes in avalanche order; with three or fewer debts from the start it behaves as avalanche throughout.
The simulation rests on four stated assumptions. One: interest compounds monthly — balance times APR divided by 12, applied before payments. Two: when a minimum is left blank it is estimated as the largest of 2% of the balance, one month's interest plus 1% of the balance, or $25, capped at the balance — an industry-typical approximation, not any lender's exact formula. Three: every simulation stops at 600 months, even if balances remain. Four: all internal math uses full double precision with no per-month rounding; displayed amounts are rounded half-up to the nearest cent after totals are computed.
One limitation to know: the engine uses the nominal APR divided by 12 as the monthly rate, which matches the standard US credit-card convention. Loans that accrue with a daily periodic rate produce slightly different month-to-month figures.
Worked example
Inputs: Debt A, balance $500, APR 24.99%, minimum $25 (entered); Debt B, balance $2,000, APR 12%, minimum $50 (entered); monthly budget $300. Snowball targets A first (smallest balance). Each month: interest first, then minimums ($25 to A, $50 to B), then the $225 remainder to A.
| Month | A interest | A paid | A end | B interest | B paid | B end |
|---|---|---|---|---|---|---|
| 1 | $10.41 | $250.00 | $260.41 | $20.00 | $50.00 | $1,970.00 |
| 2 | $5.42 | $250.00 | $15.84 | $19.70 | $50.00 | $1,939.70 |
| 3 | $0.33 | $16.17 | $0.00 | $19.40 | $283.83 | $1,675.26 |
Month 1: A interest $500 × 0.2499 ÷ 12 = $10.4125, balance $510.4125; B interest $2,000 × 0.12 ÷ 12 = $20.00, balance $2,020.00. Minimums leave A at $485.4125 and B at $1,970.00; the $225 remainder clears A down to $260.4125, displayed $260.41. Month 2: A interest $260.4125 × 0.020825 = $5.4231, balance $265.8356; after the minimum and the $225 remainder, A ends at $15.8356, displayed $15.84. Month 3: A interest $0.3298 takes it to $16.1654; the entered minimum is capped at the balance, so A is paid $16.17 and clears. The $8.83 of unspent minimum joins the $225 remainder, and B receives $283.83 total, ending at $1,675.2624, displayed $1,675.26. From month 3 on, A's freed $250 per month flows to B — the rollover the schedule shows as B's rising payment.
Frequently asked questions
What is the debt snowball method?
It is a payoff ordering rule: each month, after all minimums are paid, any remaining budget goes to the unpaid debt with the smallest balance. When the target clears, its whole payment rolls into the next smallest balance the following month. The ordering is rebuilt monthly from the balances still owed.
How are ties broken in the snowball order?
Debts are sorted by balance from smallest to largest; when two balances are equal, the debt with the higher APR is targeted first. After that, the next unpaid debt in the same order receives any leftover money, repeating until the month's budget is spent.
Does the snowball method change which debt gets paid first over time?
Yes. Because the sort runs on remaining balances each month, a debt that starts larger can fall below the others as it is paid down, and cleared debts drop out of the ordering entirely. That monthly re-sorting is why the per-debt payoff months in the schedule matter.
Will snowball cost more in interest than avalanche?
At the same monthly budget, the avalanche order never results in more total interest than snowball, because interest accrues as balance times APR divided by 12 and avalanche aims extra payments at the highest APR first. The comparison table on the home page shows the exact difference for your numbers.
What if I cannot cover all my minimum payments?
The calculator shows a shortfall figure, the gap between your total minimums and your budget, and distributes the budget across minimums in proportion to their amounts. No extra payment goes to a target that month, and the page presents the shortfall as a number without commentary.
Can I add extra payments to specific debts?
Yes. The what-if panel accepts an extra monthly amount per debt and one-time lump sums in chosen months. Extras are capped at the remaining balance, and any unspent portion joins the cascade pool that flows to the current target debt and then onward in snowball order.