Worked illustration
Snowball or avalanche: same extra hundred pounds, two different stories.
Both methods assume you can pay every contractual minimum and still have money left. If you cannot, stop here and read the budget page, then speak to a free adviser. The arithmetic below is a teaching model, not a quote from a lender.
What the names mean
The snowball puts the extra money onto the smallest balance first, while minimums continue on the rest. When the small balance disappears, its old minimum joins the extra and rolls onto the next smallest. The point is a finished account you can see. The avalanche puts that same extra onto the highest interest rate first, regardless of size. The point is less interest paid to lenders.
Neither method is a regulated product. You can run either yourself if, and only if, priority bills are current, the minimums are affordable, and you are not relying on new borrowing to make the payments. A debt management plan is a different creature: one payment, usually shared out by size of balance, often with a request that interest stops. Do not mix the labels.
The Rowan illustration
Rowan is not a person who wrote to us. The name marks a composite we can calculate in public without using anyone’s file. Rowan rents, lives in England, and after rent, council tax, energy, food, transport and a small seasonal pot can put £317 a month toward five non-priority debts. Of that, £217 covers the minimums we assigned for the model, and £100 is the extra. The debts total £8,580.
We charge interest each month as balance times APR divided by 12. Real credit cards often compound daily, and overdrafts are priced in ways this model simplifies. A personal loan in real life usually has a fixed contractual payment rather than a “minimum plus extra” dial. We froze the loan’s minimum at the figure below so the comparison stays readable. Do not take these minimums as what a lender would actually ask.
In month one, before any extra is aimed, interest on the five balances comes to about £168.45. That is why paying only the minimums feels like walking through wet cement: a large share of each payment is the price of last month, not the debt itself.
Snowball order
Smallest balance first. Cleared in 39 months. Interest paid £3,737.57.
| Debt | Balance | APR | Minimum | Cleared |
|---|---|---|---|---|
| Store card | £420 | 34.9% | £15 | Month 4 |
| Catalogue | £860 | 29.9% | £22 | Month 11 |
| Overdraft | £1,800 | 39.9% | £40 | Month 26 |
| Personal loan | £2,400 | 7.9% | £78 | Month 29 |
| Credit card | £3,100 | 22.9% | £62 | Month 39 |
Avalanche order
Highest rate first. Cleared in 39 months. Interest paid £3,486.32.
| Debt | Balance | APR | Minimum | Cleared |
|---|---|---|---|---|
| Overdraft | £1,800 | 39.9% | £40 | Month 18 |
| Store card | £420 | 34.9% | £15 | Month 20 |
| Catalogue | £860 | 29.9% | £22 | Month 25 |
| Credit card | £3,100 | 22.9% | £62 | Month 39 |
| Personal loan | £2,400 | 7.9% | £78 | Month 35 |
What the two runs actually show
In this particular mix the diary length does not change. Both orders finish in 39 months, because the large balances still have to be walked down after the expensive ones are gone, and the loan’s modest rate does not dominate the clock. The cost does change. The avalanche pays £251.25 less interest than the snowball. That is real money, and it is also not a fortune next to £8,580 of principal. A household that will only stick to a plan if an account hits zero in the first season may reasonably prefer the snowball and accept the extra interest. A household that can tolerate a quiet first year while the overdraft shrinks will usually prefer the avalanche.
The overdraft is the expensive one here, at 39.9% APR in the model, but it is not the smallest. Snowball therefore leaves it until third, after the store card and the catalogue. Avalanche attacks it immediately and clears it in the first half of the plan. That single sequencing choice is most of the £251.25 gap. If your own highest rate is also your smallest balance, the two methods are the same plan wearing two names.
Where both methods are the wrong tool
- Priority arrears. Extra money goes to the council, the landlord or the supplier before it goes to a catalogue, unless an adviser has set a different safe order for a specific enforcement threat.
- No surplus. If minimums already exceed what is left after housing and food, snowball maths is fiction. Relief routes, not a sharper spreadsheet, are the conversation.
- Joint debts and debts in someone else’s name. You cannot avalanche a balance you are not allowed to pay down, and you should not drain a joint account without the other person understanding it.
- Accounts that are already with enforcement agents or with a debt collection claim form. Do not set up a private payment race against a court timetable. Take the form to advice before the reply deadline.
- Using a new card to “free up” the minimums. That is refinancing by accident, and it usually recreates the pile.
A practical way to run the one you choose
List every non-priority balance, the APR if you can find it on a statement, and the minimum actually being asked this month. Automate the minimums on the day you are paid, then make the extra payment manually to the target account so you notice it. When an account closes, close the card or ask for it to be blocked if spending is the risk. Recalculate once a year, or sooner if income drops. If a month arrives when the extra cannot be paid, protect the priority bills and the minimums you can, and do not borrow the difference from a payday lender to keep the chart pretty.
If you want a second pair of eyes on whether a surplus really exists, that is debt advice, and it is free from the organisations listed on our home page. Cierzoxora will not check your figures by email. We would be guessing, and guessing with other people’s debts is how harm starts.