How does the debt snowball method work?

Full answer

The debt snowball method, popularised by financial commentators as a behaviourally-focused alternative to the mathematically optimal approach, prioritises psychological wins over pure interest-cost minimisation. **How the method works step by step** List all your debts from smallest to largest balance, regardless of their interest rate. Continue making minimum payments on all debts. Direct any extra money you have available toward the SMALLEST balance debt until it is fully paid off. Once cleared, take the amount you were paying toward that debt (minimum payment plus any extra) and add it to the minimum payment on the next-smallest debt, creating a growing ("snowballing") payment amount as each debt is cleared in turn. **Why smallest-balance-first, not highest-interest-first** This differs from the "debt avalanche" method, which prioritises the highest-interest-rate debt first regardless of balance size -- the avalanche method is mathematically optimal (minimising total interest paid over time), but the snowball method's quick early wins (clearing a small debt entirely, even if it has a low interest rate) can provide significant psychological motivation and a visible sense of progress that helps some people stick with their debt repayment plan more consistently. **The behavioural case for the snowball method** Proponents argue that personal finance is often more about behaviour and sustained motivation than pure mathematics -- if the psychological boost of quickly eliminating a debt (even a small one) helps someone stay committed to their overall debt repayment plan rather than losing motivation and giving up, the snowball method can produce a better real-world outcome despite costing more in total interest. **The mathematical cost of choosing snowball over avalanche** Because the snowball method does not prioritise high-interest debt, you will generally pay more total interest over the full repayment period compared with the avalanche method, particularly if your smallest debts happen to have low interest rates while larger debts carry high rates -- the exact difference depends on your specific mix of debt balances and interest rates. **Worked example** Someone has three debts: Card A £500 at 22% APR, Loan B £3,000 at 8% APR, Card C £1,200 at 25% APR. Under the snowball method, they would attack Card A first (smallest balance, £500), then Card C (£1,200), then Loan B (£3,000) -- despite Card C's 25% APR being higher than Loan B's 8%, the snowball method tackles based on balance size, not interest rate, so Loan B (the largest balance) is paid off last even though it accrues interest at a much lower rate throughout. **Choosing between snowball and avalanche** If you are confident in your ability to stay disciplined regardless of visible quick wins, the avalanche method (highest interest rate first) will generally save you money -- if you have previously struggled to maintain motivation on longer-term financial goals, or find visible progress important for staying committed, the snowball method's psychological benefits may outweigh its higher total interest cost. **Practical tip** Use the Debt Payoff calculator to compare both the snowball and avalanche methods side by side for your specific debts, seeing both the total interest cost difference and the projected payoff timeline for each approach, then choose whichever method you are most likely to actually stick with consistently, since a strategy you abandon partway through provides no benefit at all.

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