How Credit Card Interest Works and How to Pay It Off Faster

A credit card is the most convenient loan most people have, and one of the most expensive. The interest rate is high, it is charged every day, and the minimum payment is set so that the balance falls slowly. Understanding exactly how the charge is worked out makes it much easier to decide how much to pay and when.

APR, the daily rate and the average daily balance

The APR (annual percentage rate) is the yearly price of borrowing. Issuers convert it to a daily periodic rate by dividing by 365. At 24% APR the daily rate is 0.0658%.

Each day, the card company records your balance. At the end of the billing cycle it adds those daily balances and divides by the number of days to get the average daily balance. The interest for the cycle is the daily rate multiplied by the average daily balance and the days in the cycle. Some issuers compound daily, so unpaid interest also starts earning interest immediately. Your cardholder agreement says which method applies.

A rough shortcut is to divide the APR by 12 for a monthly rate. At 24% that is 2% a month, so a $5,000 balance adds about $100 in interest each month.

The grace period

Most cards give a grace period: if you pay the whole statement balance by the due date, purchases from that cycle carry no interest. This only works if you pay in full. Once you carry a balance, the grace period is typically lost, and new purchases start collecting interest from the day you make them until you clear everything. Cash advances and balance transfers generally have no grace period at all.

Why minimum payments keep you in debt

Take a $5,000 balance at 24% APR. Assume the minimum is the interest plus 1% of the balance, with a floor of $15, which is a common formula. The first minimum payment is $150.00.

Because the minimum shrinks as the balance shrinks, the balance falls more and more slowly. Compare that with fixed payments of $150 and $250 a month:

View the numbers behind the payoff chart

Payment plan	Time to pay off	Total interest	Total paid
Minimum (interest + 1%)	23.8 years	$9,332	$14,332
$150 a month	4.7 years	$3,322	$8,322
$250 a month	2.2 years	$1,449	$6,449

US card statements are required to show how long it would take to pay off the balance with minimum payments only, and the monthly payment that would clear it in 36 months. Check yours: it is the quickest reality check available.

How much the rate matters

The rate drives how long a given payment takes. At $200 a month, the same $5,000 balance takes 25 months at 0% and 40 months at 30%.

Ways to pay it off faster

• Pay a fixed amount, not the minimum. Choose a payment you can afford and keep it the same even when the minimum falls.
• Avalanche or snowball. With several cards, paying extra on the highest-rate card first (avalanche) saves the most interest. Paying the smallest balance first (snowball) costs somewhat more but can be easier to stick with. Our Debt Payoff Calculator compares both.
• Balance transfer. A card with a low or 0% introductory rate can save a lot, but there is usually a fee of about 3% to 5% of the amount moved, the rate rises when the offer ends, and new purchases may not get a grace period.
• Consolidation loan. A fixed-rate personal loan at a lower rate than your cards turns revolving debt into a fixed schedule, so long as you stop adding to the cards.
• Call your issuer. It costs nothing to ask for a lower rate or a hardship plan.

Mistakes to avoid

• Paying only the minimum for months because the bill "looks manageable".
• Making new purchases on a card with a balance and assuming they are interest-free.
• Using cash advances, which usually carry higher rates, fees and no grace period.
• Missing a payment, which can add a late fee and may raise your rate.

Common questions

Sources and further reading

• CFPB: How does my credit card company calculate the amount of interest I owe?
• CFPB: What is a grace period for a credit card?
• CFPB: What is a balance transfer fee?
• CFPB: Credit cards key terms

This guide is for general education and is not financial advice. The balance, rate and minimum-payment formula are illustrations; your card agreement sets the real terms.