About this calculator

Avalanche vs Snowball is a free, no-login UK debt payoff calculator. Enter your debts — credit cards, store cards, personal loans, overdrafts — and it shows you side by side how much interest you'd pay and how long it would take using the debt avalanche method versus the debt snowball method. The goal is to give you accurate numbers so you can make an informed choice, not to upsell you anything.

Why we built it

Most debt calculators we found were either US-focused (wrong currency, wrong regulatory context), cluttered with ads, or required you to create an account before they'd show you anything useful. We wanted a clean, fast tool built for UK credit cards and loans that anyone could use in under two minutes, with no sign-up and nothing to install.

We also wanted the blog articles to be genuinely useful — worked examples with real UK APRs, explanations of why the maths works the way it does, and honest comparisons of the two methods rather than just telling everyone to use the avalanche because it's "mathematically optimal." Sometimes the snowball is the right call, and we try to explain when and why.

How the calculator works

The calculator uses standard monthly compound interest arithmetic — the same maths your credit card issuer uses. Each month it applies one-twelfth of your annual APR to the current balance, subtracts your payment, and moves to the next month. For the avalanche method it directs any extra payment above minimums to the debt with the highest APR; for snowball it directs the extra to the smallest balance. Both methods continue until every debt is paid off.

The results — total interest paid, debt-free date, and monthly balance chart — update in real time in your browser. No data is sent to any server. Everything runs locally on your device, so your debt figures stay private.

What we are (and aren't)

This is an educational tool, not regulated financial advice. The calculator is accurate for the inputs you provide, but your actual payoff will depend on factors it doesn't model: whether your minimum payment changes as your balance falls (many UK card issuers recalculate minimums each month), any payment holidays, charges, or balance transfers you make along the way, and so on.

We are not a debt advice charity, a lender, or a regulated financial adviser. If you're struggling with debt — missing payments, feeling stressed about money, or unsure where to start — please contact one of the free UK debt advice services below. They are staffed by trained advisers, are completely free to use, and are authorised by the Financial Conduct Authority.

Affiliate disclosure

Some articles on this site may contain affiliate links — for example, links to balance transfer credit cards. If you apply for a product through one of those links, we may receive a commission from the lender at no extra cost to you. We only ever link to products where they're genuinely relevant to the topic being discussed, and our editorial content is not influenced by commercial relationships. The calculator itself is and will always be free with no ads embedded in it.

Contact and feedback

If you spot a calculation error, a broken link, or an article that's out of date, please let us know. You can reach us at hello@avalanchevssnowball.co.uk. We can't offer personal debt advice — for that please use the resources above — but we do read every message and fix errors promptly.