#How the two strategies differ
Both the avalanche and snowball methods start the same way: pay the minimum on every debt, then direct every spare dollar at one target. The only difference is which debt you target first.
Avalanche targets the highest interest rate. Because interest is the only thing making the debt grow, killing the fastest-growing balance first mathematically minimises total interest and, usually, total time.
Snowball targets the smallest balance. It costs more in interest, but it clears whole accounts sooner, and a body of consumer behaviour research suggests people who see accounts disappear are meaningfully more likely to finish the plan.
This calculator runs both simulations on your real numbers, so you can see exactly what the motivational choice costs. Often the gap is a few hundred dollars and a month or two — at which point snowball is clearly the right answer. Sometimes it is several thousand dollars, and that changes the calculus.
#How the simulation works
For each month the model:
- Accrues interest on every balance at
APR ÷ 12 - Applies each debt's required minimum payment
- Directs all remaining budget — your extra payment plus the minimums freed up by debts already cleared — at the current target debt
- Rolls any overflow to the next debt in priority order
That third step is the "snowball" effect that gives both methods their power. When your $210 credit card minimum disappears, that $210 does not go back into your spending. It joins the attack on the next debt, so your effective payment accelerates every time an account closes.
#Interpreting your results
The debt-free date is the headline, the interest total is the scoreboard. If both methods finish within a month or two of each other, take the snowball. If avalanche saves more than about 5% of your total balance, the maths deserves to win.
Your extra payment is the single most powerful lever. Try changing it by $100 and watch the payoff date move. On typical consumer debt loads, an extra $100 a month often removes eight to fourteen months from the timeline. Nothing else in the model — not the ordering strategy, not a modest rate change — comes close to that effect.
A lump sum is worth more than it looks. Applied to your highest-rate debt today, a tax refund or bonus removes not just the principal but every future month of compounding on it.
#Should you consolidate?
Consolidation only helps if the new rate, including origination fees, beats your blended current rate, and if you genuinely stop using the cleared cards. To test it honestly, delete your existing debts here, enter the consolidation loan as a single debt with its real APR and fee-adjusted cost, and compare the payoff date against your current plan. Many balance-transfer offers look brilliant until you include the 3% to 5% transfer fee and the rate after the promotional window closes.
#Debt payoff versus investing
A rough hierarchy that survives most circumstances:
- Build a starter emergency fund of about one month of expenses — without it, the next surprise goes straight back onto a credit card
- Capture any full employer retirement match, which is an immediate 50% to 100% return
- Attack anything above roughly 8% APR aggressively, because no low-risk investment reliably beats that after tax
- Below 5% APR, splitting between repayment and investing is defensible
- Keep the emergency fund growing alongside
#Common mistakes
- Paying a little extra on everything. Spreading $300 across five debts is dramatically slower than putting all $300 on one. The model will show you the difference.
- Forgetting the minimum rises with the balance. Card minimums are typically a percentage of the balance, so they fall as you pay down. This model uses the minimum you enter, which is slightly conservative — real payoff is usually marginally faster.
- Not cutting up the card. Every simulation here assumes no new borrowing. Adding to a balance you are attacking resets the entire plan.
Once the debts are gone, redirect the same payment into savings. Model what that becomes with the rent vs buy calculator or size the protection your family needs with the life insurance calculator.