Debt Repayment Calculator: Avalanche vs Snowball

Priority debts come first. Citizens Advice says you should work out which of your debts are priority debts, such as rent or mortgage arrears, council tax and energy bills, and deal with them first. This calculator is meant for what Citizens Advice calls non-priority debts: credit card and store card debts, payday and other unsecured personal loans, catalogue debts and overdrafts.

The two methods. Avalanche puts any money above the minimum repayments towards the debt with the highest APR. Snowball puts it towards the debt with the smallest balance. In both, the minimum repayment is made on every debt each month. The results show which one costs less and finishes sooner for your own figures.

Each month. Interest is added to every open balance. The minimum repayment is then made on every debt, and the rest of your monthly total (all minimums plus your extra amount) goes to the target debt. Once a debt is cleared, its minimum repayment isn't dropped: it rolls into the next target, so your monthly total stays the same until everything is repaid.

Order. Avalanche targets the highest APR first (on a tie, the smaller balance). Snowball targets the smallest starting balance first (on a tie, the higher APR). The order is set from the figures you enter and doesn't change along the way.

Interest simplification. The calculator treats the APR as a yearly rate and charges balance × APR ÷ 12 once a month. Your lender's own calculation may differ, so your statements may show slightly different amounts. It also assumes your APRs and minimum repayments stay as entered, that you don't borrow more and that no charges are added.

Limits. The schedule stops at 600 months (50 years). If your total monthly repayment doesn't cover the interest added in the first month, no plan is shown, because the total balance would never go down.

If you're struggling. If you can't keep up, Citizens Advice explains that you can write to your creditors and ask them to stop adding interest and charges while you work out what to do. GOV.UK suggests you speak to a debt adviser to help you choose the best way to deal with your debt, and the FCA points out that firms who give debt advice must be authorised by the FCA and follow its rules.