The two methods in one paragraph each
Debt snowball. Pay every minimum, then throw every spare pound at the card with the smallest balance. When it's gone, roll its old minimum into the next smallest. You clear accounts quickly, which feels great and keeps you going.
Debt avalanche. Pay every minimum, then throw every spare pound at the card with the highest APR. You'll usually pay less interest overall, but the first "win" can take longer to arrive.
Worked UK example
Three UK sub-prime cards — typical balances and APRs from Aqua, Vanquis and Capital One — and £150/month spare on top of the minimums:
- Card A: £450 @ 48.9% APR, £15 minimum
- Card B: £770 @ 39.9% APR, £25 minimum
- Card C: £170 @ 34.9% APR, £10 minimum
Snowball order: C → A → B. You clear Card C in about 2 months — a real, visible win — then pile onto A, then B.
Avalanche order: A → B → C. You kill the 48.9% APR first, so less of every payment is eaten by interest. Total interest paid is lower; total months are similar or slightly fewer.
Which should you pick in the UK?
- Pick snowball if you've stopped and restarted before, your debts are mostly small, or you need a quick morale boost.
- Pick avalanche if your highest APR is genuinely punishing (35%+ on a UK sub-prime card or a store card), and you can stick with the plan for 6+ months without needing a "win" to stay motivated.
- Hybrid: clear one tiny balance for the morale boost, then switch to avalanche. CrashFlow lets you flip between strategies and see the difference in months and interest before you commit.
Things people miss
- A 0% balance transfer beats both methods if you qualify. Move the highest-APR balance to a 0% card, pay the transfer fee (usually 2–4%), and avalanche from there.
- Always keep paying every minimum. Missing a minimum can void a 0% promo rate and hurt your credit file.
- Build a £500–£1,000 buffer first if you don't have one. Without it the next surprise bill goes straight back on a card.
- If you're falling behind, talk to StepChange or Citizens Advice — both are free.
Doing this in CrashFlow
Add your debts once, set your spare amount, and CrashFlow shows avalanche vs snowball side by side — months to debt-free, total interest, and the order to pay. Toggle the strategy on the dashboard; no spreadsheet needed.