Credit Card Interest Calculator — See What It Costs Per Day

Credit Card Interest Calculator — See What Your Card Costs Per Day

I used to think of my credit card interest as an abstract number on a statement. £67.43 this month. It meant nothing to me. Then someone showed me the daily figure. £2.25 per day. Every day. While I slept. While I worked. While I paid my minimum payment that barely touched the interest. The daily number made it real in a way the monthly statement never did.

This calculator shows your interest accruing in real time — per second, per hour, per day. It then runs three scenarios: minimum only, an extra £50 per month, and your chosen extra payment. The difference in years and total interest between those three scenarios is where the real value is.

How Credit Card Interest Is Calculated

The calculator uses the exact daily average balance method — the same method your lender uses. Your APR is divided by 365 to get a daily rate. That daily rate is applied to your balance every single day. This is why paying your balance down — even by a small amount — saves you more than the nominal interest rate suggests. Less principal means less interest accruing every day.

The Minimum Payment Trap

Minimum payments are designed to keep you in debt for as long as possible. On a £3,000 balance at 24.9% APR with a £75 minimum payment, you will be paying for over seven years and hand over more than £3,700 in interest on top of the original balance. Use our Minimum Payment Trap Calculator to see your exact figures.

The Balance Transfer Option

A 0% balance transfer card moves your existing credit card debt to a new card at 0% interest for 12–24 months. Transfer fee is typically 2–3%. If you can clear the balance before the 0% period ends, this is almost always cheaper than staying on a high-APR card. The calculator shows you this comparison automatically — look for the balance transfer section in your results.

Frequently Asked Questions — Credit Card Interest Calculator

What is the average credit card APR in the UK in 2026?

The average UK credit card purchase APR in 2026 is approximately 24.7%. Rates range from around 18% for cards targeting customers with good credit to over 39% for cards targeting customers with poor credit history.

How does daily interest work on a credit card?

Your APR is divided by 365 to get a daily periodic rate. That rate is multiplied by your daily balance. The daily interest charges accumulate throughout your billing cycle and are added to your statement balance. If you pay your balance in full each month before the due date, you typically pay no interest at all.

Does making an extra payment mid-month save interest?

Yes — significantly. Because interest accrues daily on your balance, reducing your balance earlier in the month means fewer days of interest on a higher balance. Even moving your payment date earlier in the month — so your balance is lower for more days — saves measurable interest over a year.

When does a balance transfer make sense?

When you can realistically clear the transferred balance before the 0% period ends, the transfer fee (2–3%) is less than the interest you would pay on your current card, and you will not spend on the cleared card or the new card during the 0% period.

What happens to my credit score when I pay off a credit card?

Paying off a credit card improves your credit utilisation ratio — which typically improves your credit score. Keep the card open after paying it off — closing it reduces your available credit and can temporarily hurt your score. See our Credit Utilisation Calculator to model the exact impact.