If you have more than one debt — a credit card here, a loan there, maybe a store card you forgot about — the order you pay them off in makes a real difference to both your wallet and your motivation. This calculator compares the two proven strategies, avalanche and snowball, side by side, so you can see the debt-free date and total interest for each and choose the one you will actually stick to.

How it works

List each debt with its balance, interest rate (APR) and minimum payment. Enter the total amount you can put towards debt each month. The calculator assumes you pay the minimum on everything, then throws every spare pound or dollar at one target debt until it is gone, then rolls that whole payment onto the next one. The difference between the strategies is simply which debt gets targeted first.

Avalanche: target the highest interest rate first. Snowball: target the smallest balance first. Everything else is identical.

How the calculation works

Interest is charged on each balance every month, so a debt at 24.9% APR costs you roughly 2% of its balance every month it survives. The avalanche method minimises total interest mathematically, because every spare payment kills the most expensive debt first.

The snowball method ignores rates and clears the smallest balance first. That is never the cheapest route on paper, but it produces quick wins — an account closed, one less minimum payment — and research on real borrowers consistently finds that people using snowball are more likely to clear their debts completely, because the early victories keep them going. The calculator shows you the exact cost of that motivation, so you can decide whether it is worth it.

Worked example

You owe £6,000 across three cards and can pay £300 a month in total:

• Card A: £800 at 19.9% APR, minimum £25
• Card B: £2,200 at 24.9% APR, minimum £55
• Card C: £3,000 at 0% (balance transfer, 12 months left), minimum £75

Minimums total £155, leaving £145 spare each month.

Avalanche order (B → A → C): the spare £145 plus B’s £55 minimum (£200 total) attacks Card B, clearing it in about 12 months. Then £225 rolls onto Card A, gone in roughly 4 more months, then everything hits Card C. You are debt-free in about 21 months, paying around £460 in interest.

Snowball order (A → B → C): Card A disappears in about 4 months — an early win — then the freed money attacks B. Debt-free takes about 22 months with roughly £540 in interest.

The difference here is about £80 and one month. Avalanche wins on cost; snowball wins on momentum. When balances and rates are similar, the gap is small — when one debt has a much higher rate than the rest, the gap grows and avalanche pulls ahead.

Tips

• Protect 0% deals. If a balance-transfer card is in the mix, make sure your plan clears it before the promotional rate expires, whatever strategy you pick — the jump to the standard APR is brutal.
• Never miss a minimum payment. A missed payment can mean late fees, a lost promotional rate and a mark on your credit file. Automate every minimum by direct debit, then make your extra target payment manually.
• Watch for the debt-free date, not just interest. If the two strategies finish within a month or two of each other, pick the one that feels more motivating. A plan you follow beats a perfect plan you quit.
• Stop adding to the cards. Both strategies assume balances only fall. Even small new spending at 24.9% APR will undo weeks of progress.
• If minimums alone are unaffordable, get free help early. In the UK, charities such as StepChange and National Debtline offer free, impartial debt advice. In the US, look for a non-profit NFCC member credit counsellor.

FAQ

Which method is actually better?
Avalanche is always cheaper or equal in pure maths. Snowball is often better in practice because people stick with it. Compare both results above: if the interest difference is small, choose snowball for the motivation; if it runs to hundreds, choose avalanche.

What if I can only afford the minimum payments?
Then neither strategy gets going, because there is no spare money to aim at a target debt. Focus on increasing the total payment — even £20 extra a month aimed at one card starts the roll-down effect — or seek free debt advice.

Should I use savings to pay off debt?
For high-APR debt, usually yes, after keeping a small emergency buffer. Paying 24.9% APR while earning 4% on savings loses you money every month. Keep £500–£1,000 aside so a surprise bill does not go straight back on the card.

Does the order affect my credit score?
Not directly. What matters is paying every minimum on time and reducing your overall credit utilisation. Closing a small card early with snowball can briefly change your utilisation mix, but the effect is minor compared with clearing the debt.

Should I consolidate my debts into one loan?
It can help if the loan’s APR is lower than your cards’ rates and you close or stop using the cards. It hurts if you keep spending on the cards and end up with the loan and the card balances. Run the numbers both ways before deciding.

This calculator is for guidance only and does not constitute financial advice. If you are struggling with debt, free help is available from StepChange or National Debtline in the UK.