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Debt Payoff Calculator

Calculators · Added 15 August 2026

Enter all your debts and how much extra you can pay each month, and see when you would be debt free under each of the two common strategies. Avalanche targets the highest interest rate first and always costs less; snowball clears the smallest balance first and is easier to stick to. The calculator shows both figures rather than telling you which to pick.

Your debts
NameBalanceRate (APR %)Minimum / monthRemove

On top of all the minimums

Strategy

How to use the debt payoff calculator

  1. 1Add each debt with its balance, interest rate and minimum monthly payment.
  2. 2Enter how much extra you can put in each month on top of all the minimums.
  3. 3Choose avalanche or snowball to see that strategy's plan.
  4. 4Compare the total interest against the other strategy and against paying minimums only.
  5. 5Read the payoff order to see which debt to focus on first.

Examples

Two debts, £200 extra

Input
£5,000 card at 22% (£125 min) · £8,000 loan at 7% (£200 min)
Result
Debt free in about 2 years 3 months with avalanche

The total monthly payment is £525 — the two minimums plus the extra.

Avalanche versus snowball

Input
The same debts, snowball order
Result
Same timeframe, but more interest paid overall

Avalanche is always cheaper. Whether the gap is worth the loss of motivation is a personal call.

The cost of doing nothing

Input
The same debts with no extra payment
Result
Substantially longer and considerably more interest

The comparison against minimums-only is usually the most striking figure on the page.

About the debt payoff calculator

Why rolling the payment forward matters so much

The mechanism both strategies share is more important than the difference between them. You fix a total monthly amount — all the minimums plus whatever extra you can find — and you keep paying that same total even as individual debts disappear. The payment freed up by clearing one debt does not return to your spending; it is added to the attack on the next.

That is what produces the accelerating effect the word 'snowball' describes. Early on, most of your payment is spread thinly across minimums. As debts fall away, an increasing share concentrates on a shrinking number of balances, and the last debt is being hit with the entire budget. The final debts clear far faster than the first, whatever order you took them in.

It also explains why the comparison against minimums-only is usually so stark. Paying minimums forever means the freed-up payments are never redirected — each cleared debt just reduces your outgoings. The strategies work by refusing to take that reduction until everything is gone.

The case for each order

Avalanche's case is arithmetic and not really arguable: interest accrues fastest on the highest rate, so removing that balance first removes the most future interest. Any other order costs more. Where the difference is large — a 24% card against a 4% loan, over several years — it can run to thousands.

Snowball's case is behavioural, and the evidence for it is better than a purely rational analysis suggests. Research on consumer debt repayment has found that people who clear small balances first are more likely to stay with the plan, and completion rates matter more than optimality for anyone who might otherwise stop. Watching a debt disappear entirely is a different psychological event from watching a large balance decline slightly faster.

The useful question is not which is better in principle but how much the difference costs in your specific case. Often the two strategies produce very similar totals, because the highest-rate debt happens also to be small, and then the choice is free. When they diverge sharply, the number is worth looking at directly — which is why it appears on the results rather than being summarised as a recommendation.

What the simulation assumes

Interest is applied monthly at one twelfth of the annual rate, before payments are made. Real credit cards typically compute interest daily on the average balance, which produces a slightly different and usually marginally higher figure. Minimum payments are held constant, where most cards recalculate them as a percentage of the balance each month — holding them fixed makes the projection slightly optimistic against a card whose minimum falls.

Nothing is modelled for fees, annual charges, promotional rate expiry, penalty rates after a missed payment, or new spending. Each of those pushes the real payoff date out, and the last is the one that most often derails a plan in practice: paying down a card while continuing to use it can leave the balance flat for years.

The result is best read as the shape of the plan rather than a precise date — which debt to attack, roughly how long it takes, and how much difference the extra payment makes. Those conclusions are robust to the modelling assumptions. The exact month is not.

Frequently asked questions

What is the difference between the avalanche and snowball methods?
Both pay the minimum on everything and direct all spare money at one target debt, then roll that payment into the next when it clears. Avalanche targets the highest interest rate first; snowball targets the smallest balance first. Avalanche is arithmetically optimal — it always costs the least interest and finishes no later. Snowball clears individual debts sooner, which many people find far more motivating, and a plan you actually finish beats an optimal plan you abandon.
Which one should I use?
That depends on you rather than on the maths, which is why this calculator reports both instead of recommending one. Run your own figures: if avalanche saves you a few hundred, and clearing a small debt in three months is what keeps you going, snowball is a defensible choice. If it saves thousands, that is harder to argue away. The comparison figure on the results panel is there precisely so you can make that trade-off with a real number rather than a feeling.
Why does my payoff take longer than the calculator says?
Usually one of three reasons. Credit card minimum payments are typically a percentage of the balance, so they fall as the balance does — this calculator holds them fixed, which is slightly optimistic. Any new spending on a card you are paying down obviously extends things. And promotional rates ending, annual fees, or interest charged daily rather than monthly all push the real figure out. Treat the result as a good plan, not a guarantee.
What if the calculator says my debts never clear?
It means the total you are paying does not cover the interest those balances accrue, so they grow rather than shrink. That is a genuine result and worth knowing rather than papering over with a large month count. The options are to increase the monthly amount, reduce the interest rate through a balance transfer or consolidation, or seek help — most countries have free, non-profit debt advice services, and speaking to one early is considerably better than late.
Should I pay off debt or save first?
As a general principle, debt costing more in interest than savings earn is worth clearing first — and credit card rates make that comparison one-sided. The common exceptions are keeping a small emergency fund so a surprise does not put you straight back on the card, and taking any employer pension match, which is an immediate return no debt rate beats. Beyond that it becomes personal circumstance, and this is a calculator rather than financial advice.

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