How Credit Card Interest Works

Credit card interest is one of the most misunderstood aspects of personal finance. Most people know their APR but don't understand how daily compounding, grace periods, and minimum payments interact to keep them in debt.

Daily Compounding Explained

Credit card interest compounds daily, not monthly or annually. Your card takes your APR, divides it by 365 to get the daily periodic rate, and applies that to your balance every single day. On a 24% APR card, the daily rate is 0.0657%. On a $10,000 balance, that's $6.57 per day — or $197 per month — just in interest charges.

The Grace Period Trap

Most cards offer a 25-day grace period on new purchases — but only if you paid your previous statement balance in full. If you carried any balance, the grace period disappears and interest starts accruing on new purchases immediately. This is why partial payments are so costly.

How Minimum Payments Are Calculated

Most issuers set minimum payments at 1-2% of the balance or $25-$35, whichever is greater. On a $10,000 balance at 24% APR, the minimum payment is roughly $200. But $197 of that goes to interest, meaning only $3 reduces your actual balance. This is why minimum payments can take 25+ years to pay off a balance.

Interest vs. Principal

Every payment is split between interest and principal. Early in your repayment, almost all of each payment goes to interest. As the balance decreases, more of each payment goes to principal. This is why increasing your payment — even by $50 — has an outsized impact on your payoff timeline.