Debt snowball calculator
Pay the smallest balance first for behavioural momentum — see your payoff order, time to debt-free, and total interest under the snowball method.
Calculator debtLogic updated April 2026
This calculator runs the debt snowball strategy across all your debts: pay the minimum on every debt, throw your extra payment at the smallest-balance debt first, then cascade that minimum into the next-smallest debt when the first is cleared. It's the strategy that maximises early wins for psychological momentum, even though it doesn't always minimise total interest.
How this is calculated
Formula
Each month: balance = (balance × (1 + r/12)) − payment ; extra goes to the smallest non-zero balance ; freed minimums roll into the extra poolStep-by-step
- Sort debts by current balance ascending — the smallest debt is the first target
- For each month, accrue interest on every debt at its monthly rate, then apply the minimum payment to each
- Apply the entire extra monthly payment to the current target debt on top of its minimum
- When the target debt reaches zero, add its minimum payment to the extra pool and switch the target to the next-smallest remaining debt
- Repeat month-by-month until all debts reach zero or the simulation cap of 600 months is reached
- Track payoff order, total interest paid, and months to debt-free
- Rounding mode
- ROUND_HALF_UP
- Precision
- 20-digit internal precision (Decimal.js), rounded to 2 decimal places for display
- Logic last reviewed
Assumptions & limitations
What this calculator assumes
- Each debt accrues interest monthly at its stated annual rate
- Minimum payments are fixed for the life of each debt
- Extra payment is made consistently every month
- When a debt is paid off, its minimum payment rolls into the extra pool
- Priority order: smallest remaining balance first
- Simulation is capped at 600 months (50 years) to bound analysis
What this calculator doesn’t account for
- Does not model rate changes during the payoff period
- Does not include any new debt added during the payoff (e.g., new credit card balances)
- Does not account for promotional balance-transfer rates expiring
- Does not model behavioural lapses — assumes the extra payment is made every single month
- Does not factor in tax effects on tax-deductible debts
Worked example
A borrower has three debts and $300 of monthly extra payment available.
| Input | Value |
|---|---|
| Store card | $1,200 @ 24%, $50/month minimum |
| Credit card | $5,000 @ 18%, $150/month minimum |
| Personal loan | $10,000 @ 11%, $220/month minimum |
| Extra monthly payment | $300 |
Debt-free in ~36 months, paying off in order: store card → credit card → personal loan
Month one, the $300 extra plus the $50 minimum knocks out the store card in roughly 4 months — an early win. Its $50 minimum rolls into the extra pool, so $350 plus the credit card's $150 minimum attacks the credit card next. Once the credit card clears, the cascading pool ($300 + $50 + $150 + $220 minimum) hits the personal loan and finishes it within a few more months.
Frequently asked questions
What is the debt snowball method?
A debt-payoff strategy that orders debts from smallest balance to largest and attacks them in that order, regardless of interest rate. Every freed minimum rolls into a growing 'snowball' that hits each subsequent debt harder than the last. It was popularised by Dave Ramsey because the early wins keep people motivated through what is otherwise a multi-year grind.
Snowball vs avalanche — which saves more?
Avalanche (highest rate first) saves more total interest, mathematically. Snowball usually costs slightly more in interest but produces faster early wins. For most borrowers the cost difference is a few hundred dollars over the life of the plan — small enough that the strategy you'll actually stick with beats the one that's optimal on paper.
How do I stay motivated with snowball?
The whole point of snowball is the early wins, so lean into them: cross debts off a visible list, recalculate the projected debt-free date each time a balance closes, and celebrate the milestone. This calculator gives you a payoff order and total months — keep it open and re-run it as balances change to see your finish line getting closer.
When is snowball better than avalanche?
When the highest-rate debt has a balance much larger than the rest, avalanche can take a long time to produce its first win — and people who quit halfway lose to either strategy. Snowball is also better when your highest-rate debts and your smallest-balance debts are the same (which is common for credit-card debt) — both methods produce similar payoff orders.
What if my minimum payments are too small to cover interest?
If a debt's minimum doesn't exceed its first month's interest, that debt never reaches zero — interest grows faster than payments reduce the balance. The calculator detects this dead end and surfaces the minimum viable payment needed to make any progress. That's the floor below which no payoff strategy works.
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