Avalanche or snowball — which is better?

Mathematically, avalanche always pays the least total interest because it kills your highest-rate debt first. Snowball pays slightly more interest but gives you quick wins (clearing a small balance feels good), which can improve follow-through. If the gap is small, pick whichever you will actually stick with.

How does the extra monthly payment work?

Every month, every debt receives its minimum payment. Anything above that — your extra payment plus any minimum freed up by debts that have been paid off — goes entirely to your strategy's target debt. Once that debt is cleared, the full snowball rolls onto the next target.

What if my minimum payment doesn't cover the interest?

Without an extra payment, that debt will grow forever and the calculator marks payoff at 1,200 months (its safety cap). Adding any extra monthly payment usually rescues the simulation by routing the snowball to that debt.

Why is real-world payoff different?

This calculator assumes fixed APRs and fixed minimum payments. In reality, card minimums often decline as the balance shrinks, promotional 0% APRs expire, and daily interest compounding slightly raises the total. Treat the result as a planning estimate.