Breakdown
How it works
Avalanche targets the highest interest rate first and is mathematically cheapest. Snowball targets the smallest balance first and clears individual debts sooner, which many people find easier to stick to. The difference in interest is usually modest unless rates vary widely; consistency matters more than the method.
Formula
Worked example
Debts of 3,000 at 22%, 8,000 at 19% and 1,200 at 12% with a 500 budget: both methods clear everything in about 2 years 5 months; avalanche (3,000 → 8,000 → 1,200) costs slightly less interest than snowball (1,200 → 3,000 → 8,000).
Frequently asked questions
Which method should I use?
Avalanche if the rate gap is large (e.g. a 30% card and a 6% loan). Snowball if several small debts are weighing on you. Either beats paying minimums everywhere.
Should I consolidate instead?
A consolidation loan helps only if its APR is below your weighted average and you stop using the cards. Compare its total interest with the avalanche figure here.
Do I include my mortgage?
No — mortgage rates are much lower; prioritise consumer debt. Student loans with income-contingent repayment should also be excluded.
What if my budget does not cover the interest?
The calculator flags it. Contact a free debt charity (StepChange, National Debtline in the UK) about a payment plan before interest compounds further.