How the comparison works

The calculator protects the cash reserve first, then compares two starting choices: put the available lump sum on the card, or use it as a loan overpayment. It keeps the monthly card and loan payments the same in both projections.

The estimated cost includes card interest, loan interest and the loan overpayment charge entered. It also checks whether the card is likely to be cleared during the promotional period.

Assumptions and limitations

The loan charge is paid from the available lump sum before working out the overpayment. Any cash left after clearing the selected debt is retained, not passed to the other debt. Monthly payments stay fixed and do not roll over when one balance clears. The loan APR stays unchanged throughout the projection.

The promotion is modelled in whole months, including the selected expiry month; an actual mid-month expiry will differ. If either route cannot clear both debts within 600 months, the tool withholds the full-cost comparison. This safeguard and cash-charge treatment were checked on 1 September 2026.

This is an estimate for planning, not financial advice. Interest is modelled monthly from the APR entered. Credit-card providers may calculate minimum payments differently, rates can change, and some promotions can be lost after a missed payment. Loan settlements and partial overpayments can also be calculated differently by the lender.

Source notes checked August 2026: MoneyHelper guidance on managing credit and MoneyHelper personal-loan guidance. Check the current agreements and lender quotations before acting.

How to read the result

The lower-cost route is the projection with less estimated interest and loan overpayment charges. The difference can be small, so do not treat a few pounds as certainty. Payment dates, daily interest, card minimum-payment rules and the lender's settlement calculation can all move the real figure.

Pay particular attention to the card balance at the promotional end date. A loan-first result can still carry more practical risk if the normal card payment is not enough to clear the 0% balance in time. In that situation, try increasing the monthly card payment or protecting part of the lump sum for the card before comparing again.

If the cash reserve is zero, the warning is deliberate. Keeping accessible money for an unexpected bill can reduce the chance of paying debt down and then needing to borrow again. The right buffer depends on your household and is not calculated here.

Debt overpayment FAQs

Does a 0% credit card always come second?

Not necessarily. The loan may cost more today, but the card still needs a realistic plan to be cleared before its promotional rate ends.

Does the calculator include early repayment charges?

It applies the loan overpayment charge percentage you enter. The lender's actual quotation and agreement take priority.