What this calculator does
There are two sensible orders for paying off multiple debts. The avalanche directs spare money at the highest interest rate, which costs the least. The snowball directs it at the smallest balance, which clears individual debts sooner and is easier to stick with.
The avalanche always wins on arithmetic, but often by less than expected. With $300 a month spare against these three debts, it saves $476.25 and finishes one month sooner, which many people would trade for the momentum of clearing a debt early.
The formula
Both approaches are simulated month by month. Minimum payments are made on everything, interest accrues on each balance, and the extra payment goes entirely to whichever debt the chosen strategy targets, rolling forward as each is cleared.
| Term | Meaning |
|---|---|
| Avalanche | Extra payments go to the highest interest rate first. Mathematically optimal. |
| Snowball | Extra payments go to the smallest balance first. Clears individual debts fastest. |
| Rollover | As each debt clears, its payment joins the extra amount, which is what accelerates both methods. |
The inputs explained
| Field | What to enter |
|---|---|
| Debt balances (comma separated) | Current balance on each debt, comma separated. |
| Interest rates, same order (comma separated %) | Interest rate on each debt, in the same order. |
| Minimum payments, same order (comma separated $) | Minimum monthly payment on each debt, in the same order. |
| Extra you can put toward debt each month ($) | How much you can put toward debt each month beyond the minimums. |
When to use it
Choosing an order to pay debts off
Seeing the actual cost difference makes the trade-off concrete rather than theoretical.
Working out what extra payments achieve
Raising the extra amount shortens the timeline sharply on both strategies.
Deciding whether motivation is worth the cost
If the avalanche saves very little, the snowball's psychological benefit may be worth more.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much does the extra payment change things?
The same three debts with three levels of extra payment.
| Extra per month | Interest paid: avalanche | Interest paid: snowball |
|---|---|---|
| $100 | $7,278.91 | $8,699.03 |
| $300 | $4,331.49 | $4,807.74 |
| $600 | $2,760.47 | $2,959.08 |
Questions
Which method is actually better?
The avalanche always costs less, by definition, since it attacks the most expensive interest first. Whether it is better depends on whether you will stick with it, and research on debt repayment suggests many people do better with the snowball for that reason.
Why does the gap narrow with larger extra payments?
Because everything clears faster, leaving less time for interest rate differences to compound. When the whole plan takes 28 months instead of 60, the ordering has far less opportunity to matter.
Do minimum payments have to keep being made?
Yes, on every debt. Both strategies assume the minimums continue on all accounts and only the extra amount is directed. Missing a minimum triggers fees and damages your credit regardless of strategy.
What about consolidating instead?
Consolidation or a balance transfer can beat both methods if the new rate is genuinely lower after fees. It is worth checking separately, though it only helps if the repayment discipline continues afterwards.
For whether moving a balance helps, see the balance transfer calculator. For how balances affect your credit, see the credit utilisation calculator.