Credit cards are one of the most expensive ways to borrow money in the United States. The average purchase APR sits near 22%, which means a balance that feels small on the statement can grow by more than a hundred dollars every month if you only pay the minimum. This credit card interest calculator turns your current balance and APR into three numbers you actually need: how much interest you are being charged each day, how much you will owe next statement, and how long it will take you to climb out of debt at the payment you can afford.
Adjust the sliders and every figure updates instantly. The math follows the same average-daily-balance method that major issuers such as Chase, Citi, American Express, and Capital One use on your monthly statement, so the number you see here should line up almost exactly with the finance charge printed on your next bill.
How to Use
- Enter your Current Balance — the statement balance you are carrying over from last month. If you have multiple cards, run this once per card; interest does not blend across issuers.
- Type your APR (Annual Interest Rate), exactly as it appears in your online account under "Rates and Fees". A purchase APR and a cash-advance APR can be different; use the purchase rate unless you are actually pulling cash.
- Set your Billing Cycle Length to the number of days on your last statement. Most cycles are 28–31 days. This controls the precise billing-cycle finance charge shown in the result card.
- Expand the optional fields to set your Minimum Payment percentage — most cards ask for 1%–3% of the balance, or a flat $25–$35, whichever is larger.
- Enter a Planned Monthly Payment if you want to see the payoff timeline. Leave it at zero to just see the interest cost.
The result card breaks the charge into the daily periodic rate, the interest per day, the estimated monthly interest, the billing-cycle finance charge, the annual cost of carrying the balance, the typical minimum payment, and — if you entered a planned payment — the number of months and total interest needed to reach a zero balance.
How Credit Card Interest Is Actually Calculated
US issuers almost always use the average daily balance method. The math has three steps:
- Convert the APR to a daily rate. Divide the annual percentage rate by 365. A 22.9% APR becomes 22.9 / 100 / 365 = 0.0006274, or 0.0627% per day.
- Multiply by the balance. If your balance stayed at $5,000 all month, the daily interest is $5,000 × 0.0006274 = $3.14 per day.
- Multiply by the number of days in the billing cycle. Over a 30-day cycle that is $3.14 × 30 = $94.11.
As a handy shortcut, the monthly interest on a flat balance is simply balance × APR / 12. On $5,000 at 22.9% that is $5,000 × 0.229 / 12 = $95.42. The one-dollar gap comes from 30 vs 30.417 days (365/12); either figure is within a few cents of what your bank actually charges.
The fine print that matters: interest only applies this way if you do not pay your full statement balance by the due date. As long as you clear the statement balance every month, you get the grace period and pay zero interest on purchases. The moment you revolve a balance, the grace period disappears for new purchases too, and every swipe starts accruing interest on day one.
Why the Minimum Payment Is a Trap
On a $5,000 balance at 22.9%, the typical 2% minimum payment is about $100 per month. Of that first payment, roughly $95 is interest and only $5 actually reduces what you owe. At that pace, paying off $5,000 takes roughly 18 years and costs more than $4,000 in interest alone — nearly doubling the original purchase price.
Raise the planned payment to $200 a month and the story changes: the same balance is gone in about 35 months and the total interest paid drops to roughly $1,860. That is a savings of over $2,000 and a decade of your life. Slide the Planned Monthly Payment control upward and watch the months-to-pay-off number collapse.
Examples
Example 1 — The everyday revolver. A cardholder carries $5,000 at 22.9% APR on a 30-day billing cycle. The daily rate is 0.0627%, daily interest is $3.14, and the estimated monthly finance charge is $95.42. If she pays only the 2% minimum ($100), $95 of that first payment is interest and $5 chips at the principal.
Example 2 — A large balance stressed through the math. A small-business owner put $100,000 of inventory on a card at 20% APR. The monthly interest alone is $16,667 and the annual carrying cost is $200,000 — more than the original balance in a single year. Running this number shows immediately why a low-interest business loan or a balance-transfer card is cheaper than leaving the balance on the card.
Example 3 — The payoff effect. On the same $5,000 at 22.9%, committing to a fixed $200 monthly payment clears the balance in 35 months and costs about $1,860 in total interest. Dropping the planned payment to the $100 minimum stretches the payoff past 15 years and piles on thousands of dollars of extra interest.
Example 4 — A zero-APR balance. If your card has a 0% promotional rate, the calculator shows $0 in daily, monthly, and annual interest. Use that window aggressively: every dollar you pay during the promo period chips straight at the principal.
FAQ
How is credit card interest calculated?
Issuers convert your APR to a daily periodic rate by dividing it by 365, then multiply that rate by your average daily balance and by the number of days in the billing cycle. As a shortcut on a flat balance, monthly interest ≈ balance × APR / 12. On $5,000 at 22.9%, that is $95.42 per month.
Do I pay credit card interest if I pay the full balance?
No. If you pay your entire statement balance by the due date every month, purchases enjoy an interest-free grace period and the finance charge is $0. Interest only starts once you carry a revolved balance past the due date, and from that point new purchases also begin accruing interest immediately.
What is a daily periodic rate?
It is your APR divided by 365. A 22.9% APR becomes 0.0627% per day. That tiny daily percentage is what the issuer multiplies by your balance each day of the billing cycle to build up the monthly finance charge.
How much interest do I pay on a $5,000 balance at 22.9%?
About $95 each month, $286 over a 30-day billing cycle on a daily-basis calculation, or roughly $1,145 per year if the balance never drops. Paying only the 2% minimum ($100) means most of each payment is interest and the balance takes well over a decade to clear.
What is the minimum payment on a credit card?
Most cards ask for the greater of a percentage of the balance (typically 1%–3%) or a flat $25–$35. On a $5,000 balance at 2%, that is $100. The minimum is designed to cover the issuer's interest charge plus a sliver of principal — which is exactly why balances paid only by the minimum take years to retire.
Will transferring my balance save money?
Usually yes, if you qualify for a 0% APR balance-transfer offer. A $5,000 balance at 22.9% costs $95 per month in interest; moving it to a 12-month 0% promo card (after a 3–5% transfer fee) can save close to $1,000 over the promo window. Compare the transfer fee against the interest you would otherwise pay before you decide.
Why is my calculator number different from my statement?
Statements use the exact average of your daily balance across the cycle, including new purchases, returns, and payments. This calculator assumes a flat balance, so it is an approximation. The difference is usually under a few dollars; for an exact figure, pull the "average daily balance" line from your last statement and re-run the tool.
Disclaimer
This credit card interest calculator is provided for informational purposes only and does not constitute financial, lending, or tax advice. Estimates use the standard average-daily-balance method and assume a flat balance across the billing cycle; actual finance charges depend on your card agreement, daily balance fluctuations, promotional rates, cash-advance terms, and grace-period rules. Always confirm your exact interest cost and payoff timeline with your card issuer or a qualified credit counselor before making balance-transfer, payoff, or debt-consolidation decisions.