Debt Snowball Calculator

Build a clean payoff model from your balances, APRs, and minimum payments. Compare Snowball (smallest balance first) vs Avalanche (highest APR first), see total interest, and generate month-by-month schedules — with clear assumptions and no data stored.

For educational purposes only. This calculator provides general estimates and does not provide financial, trading, tax, or legal advice.

Runs locally in your browser. No account. No signups.

Fast Comparison (Snowball vs Avalanche)

Add your debts, set an optional extra monthly amount, and compare payoff time and interest under both payoff orders. This is arithmetic modeling — not a recommendation.

Your debts
Tip: If you’re modeling only minimum payments, leave “Extra monthly payment” at $0 and compare the two payoff orders.
This amount is added on top of all minimum payments in the model and is rolled to the current target debt each month.
Used only to estimate an illustrative payoff month. If blank, results show payoff length in months only.
Advanced assumptions & what-if sensitivity
Optional math buffer that reduces the available payment amount (e.g., 5% cushion models “not all planned money makes it every month”).
Safety cap for long timelines. Default is 600 months if left blank.
What-if sensitivity (optional)
This runs the same model with simple shifts to see how results move. It doesn’t forecast real rate changes or payment behavior.
Adds (or subtracts) from the base “Extra monthly payment” used in Compare.
Adds a flat shift to every debt’s APR in the model (e.g., +1.0 increases 18% to 19%).
Multiplies all minimum payments (e.g., 0.90 models minimums 10% lower; 1.10 models 10% higher).
Choose whether to run the what-if scenario for both methods or just one.
Educational estimates only. This calculator models debt payoff using simplified monthly interest assumptions and user-entered balances, APRs, and minimum payments, plus an optional extra monthly amount. It does not provide financial, tax, legal, or debt counseling advice and does not recommend actions. Results are illustrative summaries — not guarantees. Calculations run locally in your browser. See Disclaimer, Privacy Policy, and Terms of Use.

How This Debt Snowball Calculator Works

This page is a payoff model. You enter each debt’s balance, APR, and minimum payment. Then the calculator simulates a monthly cycle: it adds interest, applies your minimum payments, and applies any extra monthly amount to a single “target” debt based on the payoff method you choose.

The key mechanic is the rollover. When a debt reaches a $0 balance in the model, its old minimum payment doesn’t disappear — it becomes available cash flow in future months and gets rolled into the next target debt. This is what makes both Snowball and Avalanche accelerate over time.

Quick Example (Illustrative Only)

Suppose you have three debts: (1) $600 at 21% APR with a $30 minimum, (2) $2,400 at 18% APR with a $70 minimum, (3) $8,000 at 6% APR with a $160 minimum. Your total minimums are $260/mo. If you add $150/mo extra, the model uses $410/mo total payment budget.

  • Snowball: targets the $600 first. When it’s paid off, its $30 minimum rolls into the next target.
  • Avalanche: targets the highest APR first (21% in this example), rolling payments similarly.
  • Why outcomes differ: different target order changes how long high-interest balances remain outstanding.

Snowball vs Avalanche (What’s Different)

  • Snowball order: smallest balance → next smallest → …
  • Avalanche order: highest APR → next highest APR → …
  • Same engine: both methods apply all minimums, and both roll freed minimums forward when debts are paid off.
What the model is best for: comparing scenarios consistently. Change one input (extra payment, APR assumption, minimums) and compare results.
What the model is not: a personalized plan. It’s arithmetic under simplified assumptions, not individualized guidance.

Monthly Interest Assumption (Simplified)

To keep the model readable, interest is approximated monthly using APR ÷ 12. Real accounts may accrue interest daily, use statement-cycle timing, and apply payments under specific allocation rules. That’s why your real payoff can differ even with the same monthly payment total.

Inputs Checklist (What People Commonly Miss)

Before you trust the timeline, confirm these inputs

  • Balance: use the current outstanding balance you want to model (not the original borrowed amount).
  • APR: enter the rate that actually applies today (promotional APRs can change later).
  • Minimum payment: use the minimum you expect to be required (some minimums change as balances shrink).
  • Extra monthly payment: treat this as “additional payment capacity” in the model, not a promise or recommendation.
  • Fees and penalties: this model does not add late fees, annual fees, or penalty APR changes.

If your minimum payments change over time, your results will be less exact. The Advanced section includes a multiplier to help you see how sensitive the model is to minimum changes.

What the Calculator Checks For

  • Invalid inputs: negative balances, non-numeric APRs, or negative minimums are blocked.
  • Impossible payoff: if the total payment budget is too low to reduce balances under the model’s interest assumptions, the calculator flags it.
  • Safety limits: the simulation caps months to prevent runaway timelines from locking up the page.

How to Read the Output (Without Over-Interpreting It)

The comparison results summarize three numbers for each method: payoff time, total interest, and total paid. These are model outputs from your inputs — not guarantees.

Why one method can “win” in different ways

  • Avalanche tends to reduce interest: it targets high APR first, so expensive interest has fewer months to accrue.
  • Snowball can change the pacing of rollovers: paying off small balances earlier can roll minimums sooner, which can matter in some mixes.
  • Sometimes outcomes are close: if APRs are similar or balances are structured a certain way, the difference can be small.

Timing vs Interest (Why Schedules Matter)

Two plans can have similar total payoff time but different total interest. That’s because interest depends on how long balances remain outstanding, and which balances remain large during early months. The Schedule view shows the shape of the payoff month by month.

Common misread: “This payoff date is a promise.” It’s an estimate under simplified assumptions. Real accounts can differ.
Common misread: “Lower interest means always faster.” Faster payoff depends on the whole system: balances, minimums, and the rollover path.

Common Mistakes (and Why Real Life Differs)

  • Promotional APRs: a 0% promo period that ends later can change the “best” order versus a fixed APR assumption.
  • Daily interest vs monthly modeling: many lenders accrue interest daily; payments and statement cycles can change the effective math.
  • Payment allocation rules: some products allocate over-minimum payments differently (or may apply to highest APR portion first).
  • Fees: annual fees, balance transfer fees, and penalty fees aren’t included in this model.
  • Changing minimums: minimum payments may decline as balances fall. This tool treats your entered minimum as a stable baseline.
  • Rounding and cents: small differences compound over long timelines. This model prioritizes clarity over micro-precision.

Data & Privacy (Local-Only)

This calculator runs locally in your browser. Your entries are not submitted as form data and are not stored by FinFormulas for signups. For site-wide policies, see the Privacy Policy.

Related tools & reading

If you want more educational context around debt models and interest math, these pages may help for comparison:

Debt Snowball Calculator FAQ

Does this calculator store my data?

No. The calculator runs locally in your browser. Inputs are not collected for signups and are not stored by FinFormulas.

Is the payoff timeline exact?

No. Results are simplified estimates based on your inputs and the calculator’s assumptions. Real-world payoff can differ due to daily interest, statement cycles, fees, changing minimums, and payment allocation rules.

What’s the difference between Snowball and Avalanche?

Snowball prioritizes the smallest balance first. Avalanche prioritizes the highest APR first. Both roll freed-up payments to the next debt once a balance reaches zero.

What happens to the minimum payment when a debt is paid off?

In this model, the minimum payment that used to go to the paid-off debt becomes part of your available monthly “extra” and is rolled into payments on the next debt.

Will this tell me which method I should use?

No. This tool provides arithmetic outputs from your inputs so you can compare scenarios. It does not provide individualized guidance or recommendations.

Does this include fees, balance transfer costs, or penalty APRs?

No. The model focuses on balances, APRs, minimum payments, and an optional extra payment amount. Fees and changing terms can materially affect real outcomes.

Reviewed & Updated

Calculator logic and on-page content reviewed for clarity and educational accuracy. Last review: December 2025.