See exactly how your credit card balance, APR, and monthly payment interact and how much interest you'll pay. Enter your numbers to see your monthly interest charge, payoff timeline, and how a bigger payment cuts your cost.
This credit card calculator focuses on a single balance and the mechanics of how it costs you money month to month. Where a payoff calculator solves for a deadline, this tool answers a more fundamental question: given my balance, rate, and payment, what is happening under the hood? It shows the monthly interest charge, how much of your payment reduces principal, and how the payoff time stretches or shrinks as you change the payment amount. It is ideal for someone trying to understand their statement, decide on a comfortable payment, or simply see the damage that a low payment does over time. Built for US cardholders working in dollars, it uses standard monthly interest mechanics and lets you experiment freely with different payment sizes.
Enter the balance on your credit card as shown on your most recent statement.
Type in the card's annual percentage rate (APR), found in your statement's interest section.
Enter the monthly payment you plan to make on this card.
Review the monthly interest charge the calculator displays for your balance and rate.
Look at how much of your payment goes to principal versus interest each month.
Check the estimated number of months to pay off the balance at that payment.
Increase the payment amount and watch the payoff time and total interest drop.
The calculator starts by converting your APR into a monthly periodic rate, dividing the annual rate by 12. It then calculates this month's interest as balance × monthly rate. Your payment is split: the interest portion is subtracted first, and the remainder reduces your principal balance. The new, smaller balance carries into the next month, where interest is recalculated on that lower figure. This loop repeats until the balance reaches zero, and the calculator counts the months and sums the interest along the way. Because interest is charged on a shrinking balance, the early months are interest-heavy and the later months are principal-heavy. The total interest figure is simply the sum of every monthly interest charge across the full payoff period.
The result reveals the split that statements hide. Seeing that, for example, $90 of a $150 payment goes to interest explains why your balance feels stuck. The monthly interest charge is the enemy; the principal portion is your progress. The payoff time tells you how long the current payment will take, and the total interest shows the full price of carrying the balance at that pace. The most useful action is to nudge the payment upward and watch both numbers fall, often dramatically. A payment just $50 higher can cut months off the timeline and save a surprising amount of interest, because every extra dollar attacks principal directly and reduces all future interest charges. Use this to choose a payment that balances your budget against the cost of delay.
Your APR is the dominant factor, setting how fast the balance grows each month; rates across US cards average roughly 20% to 24% in 2026 (LendingTree). Your balance determines the absolute size of the interest charge. Your payment amount is the lever you fully control, and it has an outsized effect because reducing principal lowers every future interest charge. Whether your card calculates interest daily or monthly creates a small difference, with daily compounding costing slightly more. New purchases are a hidden factor, since adding to the balance increases next month's interest. Finally, the grace period matters: if you carry any balance, you typically lose the interest-free grace period on new purchases until you pay in full.
Dana carries a $3,500 balance at 22% APR. The monthly rate is about 1.83%, so her first month's interest is roughly $64. If she pays $150, only about $86 reduces principal. At that pace the balance takes around 29 months to clear and costs about $830 in total interest. The calculator makes plain that more than 40% of her early payment is pure interest.
Same $3,500 balance and 22% APR, but Dana raises her payment to $250. Now about $186 of the first payment hits principal. The payoff time falls to roughly 16 months and total interest drops to about $440. By adding $100 a month, she cuts the timeline nearly in half and saves around $390 in interest, a clear illustration of how payment size drives the entire result.
Always pay more than the interest charge shown, or your balance will never go down.
Use the calculator to find a payment that clears the card in a timeframe you can stomach, then automate it.
Avoid new purchases on a card you are paying down, since they raise next month's interest and erase progress.
If you carry a balance, remember you lose the grace period, so new purchases start accruing interest immediately.
Check whether your card compounds interest daily and, if so, pay a little earlier in the cycle to trim the charge.
Revisit the calculator whenever your rate changes, since variable APRs move with the prime rate.
It shows the monthly interest on your balance and splits your payment into interest and principal. You can see payoff time and total interest, then test how a bigger payment helps.
Your APR is divided by 12 to get a monthly rate, which is multiplied by your balance to find the interest charge. Many cards compound this daily for a slightly higher cost.
At high APRs, the interest charge consumes a large share of a small payment. Only the amount above the interest reduces principal, which is why low payments feel ineffective.
Every extra dollar attacks principal and lowers all future interest charges. Raising your payment even modestly can cut months off the payoff and save meaningful interest.
APR is the yearly rate. Monthly interest is the APR divided by 12, applied to your balance each month. The calculator handles this conversion for you automatically.
Yes. Once you carry a balance, you usually lose the interest-free grace period, so new purchases begin accruing interest right away until you pay the card in full.
Yes, it is completely free and requires no signup. Enter your balance, rate, and payment to instantly see your interest cost and payoff timeline.
Brief disclaimer: This calculator provides estimates for educational and planning purposes only. Actual interest charges, payoff times, and costs depend on your card's specific terms, rate changes, and payment timing. Results should be treated as planning guidance rather than financial advice.