The minimum payment falls as the balance falls
This is the whole trap, and it is deliberate rather than accidental. A typical UK minimum payment is the greater of about 1% of the balance plus that month's interest, or a small floor of a few pounds.
Because the percentage part is calculated on the balance, it shrinks every single month as the balance drops. The payment chasing the debt gets smaller at exactly the same rate the debt does, which is why a card that could be cleared in a couple of years instead takes decades.
Since 2011, UK credit card statements have been required to show what happens if you pay only the minimum. It is on the statement precisely because the answer is so bad. Most people never read it.
Freezing the payment is the entire fix
Take whatever your minimum is this month. Set up a standing order for that exact amount. Never let it fall.
That costs you nothing extra this month, not a penny, and it typically clears the balance in around a third of the time for a fraction of the interest. Every month the fixed amount covers more capital than a shrinking minimum would have done, and the effect compounds.
It is the highest-value, lowest-effort change available on a credit card, and it requires no negotiation, no application and no change to your budget.
When the payment never clears it at all
If what you pay does not cover the month's interest, the balance grows. Not slowly, not eventually: every month, indefinitely, with no end point at any payment level below the interest.
This tool reports that as never rather than producing a very large but finite number of months, because a big number implies there is an end and there is not. On a £3,000 balance at 22.9% the interest alone is around £57 a month, so anything at or below that is not repayment at all.
That is the point at which the card has stopped being credit and become a standing charge, and it is worth speaking to a free debt advice service such as StepChange or National Debtline rather than running another calculator.
Balance transfers, and the mistake that undoes them
A 0% transfer is usually worth doing. A fee of a few per cent against an APR in the twenties is rarely a close call, and it converts a compounding problem into a fixed deadline.
The mistake is what happens next. The new card has its own minimum, calculated on the same shrinking basis, and it will be comfortably affordable. Pay that, relax, and you arrive at the end of the promotional period with most of the balance intact and a standard rate waiting for it.
Work out what clears the balance within the promotional period, and pay that. A transfer buys you time, not a discount, and the time is only worth anything if it is used.
Stop feeding it
Spending on a card while paying it down works against you from both ends. New purchases add to the balance, and under the usual payment allocation rules your money tends to go at the more expensive portions of the debt first, so recent spending can sit behind the older balance accruing interest while you make no visible progress.
Moving day to day spending onto a debit card for a few months is not a lifestyle change worth agonising over, and it is frequently the difference between a plan that finishes and one that does not.
Common questions
Why does paying the minimum take so long?
Because the minimum is a percentage of the balance plus that month’s interest, so as the balance falls the payment falls with it. The debt is always being chased by a shrinking payment, which stretches it out for decades. That is not an accident of the arithmetic, it is how the product is designed, and since 2011 UK statements have had to show what paying only the minimum costs for exactly this reason.
What is the single easiest thing I can do?
Freeze the payment. Work out what your minimum is this month, set up a standing order for that exact amount, and never let it fall. It is identical money this month and it typically clears the balance in a third of the time for a fraction of the interest, because every month the fixed amount covers more capital than a shrinking minimum would.
What happens if my payment does not cover the interest?
The balance grows every month, indefinitely. It never clears, at any point, and no amount of patience fixes it. This tool reports that as "never" rather than producing a large but finite number, because a big number implies an end that does not exist. If that is where you are, a free debt advice service is the right call rather than a calculator.
Is a 0% balance transfer worth it?
Usually yes, and the arithmetic is rarely close: a transfer fee of a few per cent against an APR in the twenties. The trap is what happens afterwards. Transfer the balance, then pay the new and much lower minimum, and you can arrive at the end of the promotional period with most of the debt intact and a standard rate waiting. The saving only lands if you keep paying at least what you were paying before.
Does it matter that I am still using the card?
Yes, twice over. New purchases add to the balance you are trying to clear, and under the usual allocation rules your payments tend to tackle the higher rate portions first, so spending can sit behind the existing balance and keep accruing. Clearing a card is dramatically easier when it is not simultaneously being used, even if that means moving day to day spending to a debit card for a while.