Debt Payoff Calculator

What this calculator does

This debt payoff calculator simulates your actual debts month by month. Enter each balance with its APR and minimum payment, add whatever extra you can put in each month, and it returns the payoff date, total interest, and the order accounts are cleared under both the avalanche and snowball methods, measured against a minimums-only baseline.

That baseline is the most valuable output. Seeing what minimum payments alone would cost, in months and in pounds, turns the extra payment from a sacrifice into a transaction with a price attached — you are buying years back, and the calculator tells you the exchange rate.

When to use it

The obvious moment is when you hold several balances and no strategy: a credit card, a store card, an overdraft, and a loan, all meeting their minimums and none of them shrinking. The calculator shows whether the ordering choice matters for your particular mix or whether both methods produce the same sequence anyway.

It is also the right way to size the extra payment. Testing £50, £100, and £200 a month moves the payoff date in a way general budgeting advice never makes concrete. And rerun it whenever an account clears, since the roll-up reshapes what is left. If the result is that minimums alone stretch past five years, that is a signal to look at consolidation or free debt advice rather than a better ordering.

Understanding the inputs

Add each debt with its balance, APR, and current minimum payment. Include the arranged overdraft, which most people leave out and which usually carries the highest rate on the list. Getting the APR right matters most, because it determines the avalanche order — check statements rather than estimating, and note that cards often charge different rates on purchases, transfers, and cash withdrawals.

Minimum payment should be today's contractual amount. The calculator holds it fixed rather than letting it fall as the balance drops, which is both the better strategy and what happens if you set a standing order. The extra monthly payment is a single figure across all debts — the method decides where it lands each month.

How is this calculated?

debt-payoff-calculator

A worked example

Take three debts: a £6,000 credit card at 24.9 percent with a £150 minimum, a £1,200 store card at 21.9 percent with a £35 minimum, and a £3,800 personal loan at 9.9 percent paying £120. That is £11,000 owed and £305 a month in minimums, which alone would take 58 months and cost roughly £6,597 in interest.

Add £150 a month. Avalanche attacks the 24.9 percent card first and clears everything in 31 months for about £2,934 in interest. Snowball starts with the £1,200 store card and finishes in 32 months for around £3,467. Either way the extra £150 removes more than two years and over £3,000 of interest; avalanche saves a further £533.

Limitations and assumptions

The simulation assumes fixed APRs, minimum payments that do not change, no further spending on any account, and a consistent extra payment every month. In practice card rates vary, 0 percent promotional periods expire, and one unplanned expense on a card resets the schedule.

It does not model balance transfers, consolidation loans, or informal arrangements such as a debt management plan, all of which can outperform any payoff ordering. Nor does it account for the behavioural side, which usually decides the outcome. If minimums are already unaffordable, free advice from StepChange or National Debtline is the right next step.