Debt payoff calculator
Add your real debts, one by one, and see which payoff order clears them cheapest. Smallest balance first feels better. Highest rate first costs less. See what the gap actually is for your debts before you pick.
Updated for the 2026/27 tax year · reviewed
Your debts
Add every debt separately - the whole point is that the order you clear them in changes what you pay. Balance and APR are on your statement; the minimum is what you're contractually obliged to pay each month.
On top of your minimums of £405 - a total commitment of £555 a month. Both methods below assume exactly this same budget.
Clearing the highest rate first saves you
£184
in interest, across 2 years 8 months of repayments
Snowball
Smallest balance first
- Debt-free in
- 2 years 8 months
- Debt-free by
- May 2029
- Total interest
- £2,696
- First debt gone
- 5 months
Fastest first win - a whole debt gone soonest.
- 1.Store card5 months
- 2.Credit card2 years 2 months
- 3.Car finance2 years 8 months
Avalanche
CheaperHighest interest rate first
- Debt-free in
- 2 years 8 months
- Debt-free by
- May 2029
- Total interest
- £2,512
- First debt gone
- 2 years
Mathematically the cheapest route, always.
- 1.Credit card2 years
- 2.Store card2 years 1 month
- 3.Car finance2 years 8 months
Total owed
£14,950
3 debts
Monthly commitment
£555
minimums plus extra
Cheapest total cost
£17,462
everything you'd repay
Interest either way
£2,512
the unavoidable part
What you still owe, month by month
Both lines start at the same balance and commit the same money each month. The only difference is the order - which is why they separate in the middle and meet again at zero.
Debts are one part of the picture.
Quidworth puts your debts, mortgage, savings and pensions in one plan - so you can see what clearing them does to your household net worth, years ahead.
Create your free accountHow this calculator works
Rather than collapsing your debts into one balance at one average rate, this runs a real month-by-month simulation of each debt separately. Every month it charges interest on each balance, pays the contractual minimum on everything, then throws whatever is left at a single target debt. The only difference between the two methods is which debt gets that spare money first: the snowball picks the smallest balance, the avalanche picks the highest interest rate.
The important detail is what happens when a debt clears. Its minimum payment doesn't vanish from your budget - it rolls onto the next target, so the payments accelerate as you go. Your total monthly commitment stays fixed at your minimums plus whatever extra you can find, which is what makes the two methods genuinely comparable: same money, same debts, different order.
The avalanche is always at least as cheap as the snowball - that's arithmetic, not opinion, since paying down the most expensive interest first always removes the most interest. But the gap is often smaller than people expect, while the snowball clears a whole debt sooner. We show you both numbers instead of picking for you, because the method you'll actually stick to for three years beats the one that wins on a spreadsheet.
Interest is charged once a month at the rate that reproduces your quoted APR - the twelfth root of the annual figure, not APR divided by twelve, because a UK APR already accounts for compounding. Real lenders compound daily on a fluctuating balance, so treat the total as a close estimate rather than a statement. We also assume your minimum payment stays fixed; most credit cards recalculate it as a percentage each month, which the credit card interest calculator models properly.
If your minimums can't cover the interest, this tells you so rather than inventing a payoff date. That situation needs help rather than a calculator - StepChange, National Debtline and Citizens Advice all give free, impartial UK debt advice.
Questions people ask
What's the difference between the snowball and avalanche methods?
Both put every spare pound at one debt while paying minimums on the rest. The snowball targets the smallest balance first, so you clear a whole debt sooner and get visible momentum. The avalanche targets the highest interest rate first, which is always the mathematically cheaper route. The order is the only difference - the monthly commitment is identical.
Which method should I actually use?
The avalanche always costs less in interest, but usually by less than people expect - often a few hundred pounds across a few years. The snowball clears your first debt sooner, and there's a real argument that the method you'll stick with beats the one that's optimal on paper. This calculator shows you both numbers so you can decide what the difference is worth to you.
Why does clearing one debt speed up the rest?
Because the money doesn't disappear. When a debt clears, the minimum payment that was servicing it rolls onto the next target, so your payment towards that debt jumps. Each cleared debt makes the next one fall faster - which is where the 'snowball' name comes from, and why both methods accelerate towards the end.
What if my minimum payments don't cover the interest?
Then the balance grows no matter what you pay, and this calculator will tell you so rather than printing a payoff date. That's a signal to seek free help - StepChange, National Debtline and Citizens Advice all offer free, impartial UK debt advice, and none of them charge.
Last reviewed against 2026/27 UK rules. Projections are estimates for education, not financial advice. Understanding your projections.
A calculator answers one question at a time.
The planner keeps all of them next to each other, so an overpayment you model today still shows up in the pension picture in twenty years.
- Free to start
- No card needed
- Your figures carry over