What this calculator does
Find out how long it will take to pay off your credit card, and the month you'll be debt-free. Enter the same payment you plan to make each month. You'll see the total interest, and how much you'd save by paying 25% more. Or pick a number of months, and the calculator finds the payment that clears your balance in time.
Your card charges interest on whatever balance you carry. So a small monthly payment can drag even a modest balance out for years and add a lot of interest. Here, interest is added once a month, at your APR divided by 12. The yearly table and chart show your balance falling all the way to zero. Every payment above the interest gets you closer.
Where it's used
Why this math matters outside the classroom:
- Payoff timeline. A $5,000 balance at 20% APR paid down at $200 a month takes 33 months and costs about $1,522 in interest.
- Setting a deadline. Cardholders find the fixed monthly payment needed to clear a balance in 24 months instead of open-ended minimums.
- Balance transfers. Comparing payoff time at the current APR with a lower rate shows how much interest a transfer could save.
- Algebra 2 projects. Students solve for the number of payments with logarithms and check it against a month-by-month table.
Grade level and standards: Grades 11–12; Common Core State Standards for Mathematics HSA.SSE.B.4. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Choose what you want to find: how long a fixed payment takes, or the payment you need to finish by a target.
- Enter what you owe now and your card's APR, its yearly interest rate.
- Enter your planned monthly payment, or the number of months you want to be debt-free in. Then enter the date you start.
- Read the months to pay off (or the payment you need), your debt-free date, the total interest and the year-by-year table.
What the inputs mean
- Card balance
- The amount you owe today. The calculator assumes you don't make new purchases while you pay it down.
- Card APR
- The purchase APR on your statement (APR means annual percentage rate). The calculator divides it by 12 to get a monthly rate. Promotional 0% periods and penalty rates aren't included.
- Monthly payment
- The same amount you'll pay every month. It must be more than the first month's interest, or your balance never gets smaller.
- Pay off within
- A whole number of months from 1 to 600.
- Start date
- The date you begin. The first payment is counted one month later. So 35 payments starting in October 2026 end in September 2029.
Formula and method
i = APR ÷ 100 ÷ 12 each month: balance = balance × (1 + i) − payment months to pay off: n = −ln(1 − B × i ÷ P) ÷ ln(1 + i), rounded up required payment for n months: P = B × i ÷ (1 − (1 + i)^(−n)) at 0% APR: n = B ÷ P (rounded up) and P = B ÷ n
In the formulas, B is your starting balance, P is your monthly payment, i is the monthly interest rate and n is the number of payments. ln is the natural logarithm, a calculator button that helps solve for a number of months. Each month, your balance first grows by one month of interest. Then your payment comes off.
The formula for n gives the exact number of payments. You can't make part of a payment, so it's rounded up, and the last payment covers only what's left.
B × i is the first month's interest. If your payment isn't bigger than that, the balance never falls, and there's no payoff date. So instead of showing a misleading number, the calculator tells you the payment is too low.
Worked example
You owe $5,000 on a card at 22.9% APR and pay $200 a month.
- Monthly rate: 0.229 ÷ 12 ≈ 0.01908333.
- First month's interest: $5,000 × 0.01908333 ≈ $95.42, so $200 is enough to make progress.
- Exact number of payments: −ln(1 − 5,000 × 0.01908333 ÷ 200) ÷ ln(1.01908333) ≈ 34.2969.
- Round up: 35 months, with 34 payments of $200 and a final payment of about $59.78.
- Total interest: $6,859.78 paid − $5,000 ≈ $1,859.78.
Result: Starting on October 18, 2026, the card is paid off in 35 months (2 years and 11 months), by September 2029, with about $1,859.78 of interest. Paying 25% more, $250 a month, clears it in 26 months and saves about $501.56 of interest. To finish in 24 months instead, you'd pay about $261.62 a month, and interest would drop to about $1,278.84.
Understanding the result
The total interest shows what carrying the balance really costs you. Try a shorter target to see how much a bigger payment saves.
If your payment is only a little more than the monthly interest, payoff can take decades. The good news: even a small increase in your payment can cut the time a lot. The 25%-more result shows the effect for your numbers.
Assumptions and limitations
- Interest is added once a month, at APR ÷ 12, on the balance carried into each month.
- You make no new purchases, and there are no fees, cash advances or rate changes while you pay it off.
- You pay the same amount every month, on time. The last payment is only what's left.
- Amounts aren't rounded to the cent along the way.
- Card companies usually figure interest on your average daily balance. So your real interest can differ slightly from this monthly estimate.
- Minimum payments that shrink as your balance falls aren't modeled. This calculator uses a fixed payment.
- Promotional rates, balance transfer fees and several balances at different rates aren't included.
Frequently asked questions
Why does the calculator say my payment is too low?
Each month, the card adds interest of about balance × APR ÷ 12. If your payment is no bigger than that, none of it lowers the balance, so the debt never ends. Raise the payment above the first month's interest shown in the message.
Is the minimum payment enough?
Minimum payments are set to keep your account in good standing, not to clear it quickly. They shrink as your balance shrinks, so they can stretch payoff out for many years. A fixed payment above the minimum finishes much sooner.
How much should I pay to clear my card in a year?
Switch to the target option and enter 12 months. For a $5,000 balance at 22.9% APR, that's about $470.14 a month, with about $641.68 of interest. Compare that with $1,859.78 of interest at $200 a month.
Would a balance transfer or consolidation loan help?
Moving the debt to a lower rate cuts the interest. But transfers usually charge a fee, and promotional rates end. Run this calculator once at your card's APR. Then run it again at the new rate, with any fee added to the balance, and compare the total interest.
Why is the last payment smaller?
Payments come in whole months, but the balance rarely divides evenly. The final payment is the remaining balance plus that month's interest. So it's usually less than the regular payment.
Does the order of interest and payment matter?
Yes, a little. This calculator adds a month of interest and then subtracts the payment, which matches how a statement balance is usually built. Card companies that use daily balances may come out a few dollars different.
How this calculator is checked
Method: Month-by-month balance recursion with monthly compounding at APR ÷ 12; closed-form payment count n = −ln(1 − Bi/P)/ln(1 + i) and standard level-payment formula for the target mode. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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