Skip to main content
Kalcufy

Credit Card Interest Calculator

How Credit Card Interest Works

Credit card interest is the cost you pay for carrying a balance from one billing cycle to the next. Unlike simple interest, credit card interest compounds daily — meaning you pay interest on interest every single day. Your card's APR (Annual Percentage Rate) is divided by 365 to get a daily periodic rate. Each day, that rate is applied to your current balance, and the resulting interest is added to what you owe. This daily compounding effect is why credit card debt grows so quickly and why even small balances can become expensive over time. The key insight is that if you pay your full statement balance by the due date every month, you pay zero interest — the grace period protects you. But the moment you carry any balance forward, interest starts accruing on everything immediately.

How This Calculator Works

Enter your current credit card balance, your card's APR, and the amount you plan to pay monthly. The calculator simulates your payoff journey using daily compounding interest, showing exactly how long it will take to reach zero and how much total interest you'll pay. It also calculates what would happen if you only made minimum payments — revealing the shocking true cost of the minimum payment trap. Unique metrics like the true cost multiplier show how much your original purchases actually cost after interest, while the daily interest cost makes the urgency real. If you toggle on the balance transfer comparison, it calculates whether transferring your balance to a lower-rate card would save you money after accounting for the transfer fee.

Frequently Asked Questions

How is credit card interest calculated?

Credit card interest is calculated using daily compounding. Your APR is divided by 365 to get a daily periodic rate. Each day, that rate is multiplied by your current balance to determine that day's interest charge. This interest is added to your balance, so the next day you're paying interest on a slightly higher amount. At 22% APR, a $5,000 balance accrues about $3.01 per day in interest.

What is the true cost of minimum payments?

Minimum payments are designed to keep you in debt as long as possible. On a $5,000 balance at 22% APR, paying only the 2% minimum would take over 30 years and cost more than $9,000 in interest — nearly double the original balance. The minimum payment starts at $100 but shrinks as your balance decreases, meaning less and less goes to principal over time.

How can I avoid paying credit card interest?

Pay your full statement balance by the due date every month. This activates your grace period, which means no interest is charged on new purchases. If you already have a balance, you won't have a grace period until you pay it off completely. Consider setting up autopay for the full balance to ensure you never miss a payment and always avoid interest.

What is a good credit card interest rate?

Credit card rates are generally high compared to other loans. As of 2025–2026, rates range from about 14% for excellent credit to 30%+ for poor credit. A 'good' rate is below 18%, but even that is expensive for long-term borrowing. If you carry a balance regularly, a low-interest card (13–16% APR) or a 0% balance transfer card is worth considering.

Is a balance transfer worth it?

A balance transfer to a 0% intro APR card is worth it if: the interest savings exceed the transfer fee (typically 3–5% of the balance), you can pay off a significant portion during the intro period, and you won't rack up new debt. For example, transferring $8,000 with a 3% fee ($240) from a 24% APR card saves about $160/month in interest during the 0% period.

Why does my balance grow even though I'm making payments?

If your monthly payment is close to or less than the interest charged, very little goes toward reducing your actual balance. At 24% APR on a $10,000 balance, about $200/month goes to interest alone. If your payment is $210, only $10 reduces your balance — meaning it would take 83+ years to pay off. You need to pay significantly more than the interest portion to make real progress.

What is the difference between APR and daily rate?

APR (Annual Percentage Rate) is the yearly interest rate on your card. The daily periodic rate is your APR divided by 365. For example, 22% APR becomes 0.0603% per day. While 0.06% sounds tiny, it compounds every day — meaning you pay interest on yesterday's interest. Over a year, this daily compounding makes the effective rate slightly higher than the stated APR.

Does paying more than the minimum help that much?

Dramatically. On a $5,000 balance at 22% APR: minimum payments take 30+ years and cost $9,000+ in interest. Paying $150/month fixed takes 44 months and costs $1,538. Paying $300/month takes 19 months and costs $667. Every extra dollar above the minimum goes directly to principal, creating a snowball effect that accelerates your payoff.