What this credit card calculator estimates
Enter your current balance, purchase rate and the fixed amount you plan to pay each month. The calculator estimates the payoff time, total interest and total paid. It also shows the first 12 months so you can see how much of each payment is absorbed by interest.
You can include a fixed amount of new spending, but the quickest way to make a repayment plan predictable is to stop adding purchases to the balance. A payment that looks generous can make little progress when it must also cover new transactions and interest.
How the monthly estimate works
The calculator divides the annual purchase rate you enter by 12 to estimate one month's interest. It adds that interest and any new spending, subtracts the fixed payment, then repeats the process until the balance reaches zero. The last payment is reduced to the amount actually owed.
Closing balance = opening balance + monthly interest + new spending − payment
This is intentionally a planning model, not a reconstruction of your statement. UK card providers commonly calculate interest daily and may allocate payments between balances at different rates. Cash withdrawals, balance transfers, fees and promotional periods can all change the real result.
This is a nominal monthly-rate approximation. It does not derive regulated APR from dated cash flows or reproduce daily card interest. Use the purchase rate shown for the balance you are modelling, and treat an APR entered here as an approximation.
Why fixed payments beat a falling minimum
A minimum payment normally falls as the balance falls. That feels easier month by month, but it slows the reduction of principal and keeps interest running for longer. The FCA has highlighted that payments at or near the contractual minimum can lead to very long repayment periods.
For an indicative comparison, this tool estimates a minimum as interest plus 1% of the balance or £5, whichever is higher. Fees are excluded and your provider may require more. The amount printed on your statement is always the minimum you must actually pay.
Use the comparison as a behaviour prompt
Try the calculator with your current payment, then increase it by an affordable fixed amount. The difference in payoff date and total interest is often more useful than looking at the monthly payment alone. Setting a Direct Debit for a fixed amount can also avoid the automatic decline that comes with paying only a percentage of the balance.
0% balance transfers
A balance-transfer card may charge 0% for a limited period and a one-off transfer fee. To model the promotional period, enter 0% and compare the result with the number of months in the offer. If the balance will remain after the offer ends, run a second calculation using the follow-on rate. Add the transfer fee to the starting balance if it is charged to the card.
Missing a required payment can end a promotional rate. Check the offer's conditions rather than assuming the 0% period is guaranteed regardless of payment behaviour.
When the balance is not going down
If the planned payment does not cover first-month interest and new spending, this calculator stops and tells you the approximate amount needed before the balance can begin to fall. Your contractual minimum could be higher. If the minimum is unaffordable, contact the provider and a free debt-advice service promptly; borrowing more can make the position worse.
Sources and limitations
The minimum-payment explanation is based on theFinancial Conduct Authority's repayment research. Consumer guidance was checked againstMoneyHelper's credit-card guide. Calculations run locally in your browser and no balance is sent to us.