Credit Card Payoff Plan Calculator and Payment Estimate

A credit card payoff plan calculator estimates how many months it may take to repay a balance with a set monthly payment, and how much interest that payment schedule may add. Enter your balance, APR, and planned monthly payment to see an estimated payoff time and total paid; the result assumes a fixed APR and monthly calculations.

Formula

The calculator estimates the number of equal monthly payments required to repay a balance when interest accrues monthly at a constant APR. It first calculates the monthly rate, then applies the logarithmic payoff formula:

• Monthly rate, r = APR ÷ 1,200, where APR is entered as a percentage per year.
• Months, n = ceil(round(−ln(1 − r × B ÷ M) ÷ ln(1 + r), 6)).
• Total payments = n × M.
• Estimated interest = (n × M) − B.

B is the starting balance in dollars, M is the monthly payment in dollars, and n is the estimated number of monthly payments. The formula rounds the calculated time up to a whole month, because a partial final month is represented as one more scheduled payment of the entered amount. Consequently, the total and interest results are estimates based on full equal payments, not a separately calculated smaller final payment.

Worked Example

Using the calculator’s default inputs: balance B = $5,000, APR = 20%, and monthly payment M = $250.

1. Convert APR to a monthly rate: r = 20 ÷ 1,200 = 0.0166667, or about 1.6667% per month.
2. Substitute into the payoff equation: n = ceil(round(−ln(1 − 0.0166667 × 5,000 ÷ 250) ÷ ln(1.0166667), 6)).
3. Here, 1 − (0.0166667 × 5,000 ÷ 250) is about 0.666667. The unrounded result is about 26.35 months; rounding the formula’s intermediate result and then rounding up gives 27 months.
4. Total of payments = 27 × $250 = $6,750.
5. Estimated interest = $6,750 − $5,000 = $1,750.

The headline estimate is 27 months. The total reflects 27 payments of the entered amount, so it may differ from a real account’s final payment, which is often smaller when the remaining balance is below the regular payment.

Assumptions

• The APR stays fixed throughout repayment.
• Payments are made monthly, with the model treating each payment as part of a regular monthly schedule.
• Interest compounds monthly at APR ÷ 12.
• Fees, new purchases, promotional-rate changes, late charges, taxes, and other account-specific adjustments are not included.

How to Use and Read the Estimate

Use the current balance and the APR that applies to that balance, then enter the monthly amount you are examining. If an account has balances at different APRs, such as purchases and cash advances, one APR may not represent the whole account. The calculator cannot reproduce that situation with a single rate; use a weighted or separate-balance calculation only if you have the necessary account details.

The estimated months are a planning measure, not a promised payoff date. The interest output is derived from the rounded-up month count multiplied by the same payment every month. A real card issuer generally calculates interest according to account terms and daily balances, and payment dates and amounts can vary. For an exact payoff amount or date, consult the account statement or contact the issuer.

To understand how a different payment changes the estimate, calculate again with that amount while keeping the balance and APR unchanged. The comparison isolates the effect of payment size within this simplified model. It does not account for changes to spending or interest terms.

Common Problems and Limits

The monthly payment must exceed the first month’s interest for the formula to produce a finite payoff estimate. At the defaults, the first month’s interest is approximately $83.33, so a $250 payment exceeds it. A payment that is equal to or less than the interest will not reduce the balance under the model; the expression cannot produce a valid repayment time. The calculator also rejects a payment of zero because division by zero is undefined.

• Entering APR as a decimal: Enter 20 for 20%, not 0.20. The calculator divides the percentage by 1,200 to obtain a monthly rate.
• Adding new purchases: New charges increase the balance and can extend repayment. This estimate assumes no new spending.
• Assuming every month has identical interest: Actual interest can depend on daily balances, transaction timing, payment posting, and account terms.
• Interpreting total paid as an exact payoff quote: The final payment may be smaller than the entered amount, and fees or rate changes may alter the total.

Rounding also matters. This calculator rounds the computed month value to six decimal places before rounding up to a whole month. Small differences in a different calculator’s rounding convention can shift a result near an exact whole-month boundary.

Other Ways to Plan a Payoff

A fixed-payment estimate answers one specific question: what happens if the balance, APR, and payment remain as entered? A month-by-month amortization schedule can show the changing balance and interest after each payment, but it still relies on its stated assumptions. If there are multiple cards, calculate each account separately when their APRs differ, then consider the combined monthly outflow without treating the separate estimates as exact account quotes.

A payoff plan can also change if the payment varies from month to month. In that case, this calculator’s level-payment formula is not a precise model; a schedule with each month’s actual payment and applicable rate is more suitable. Check statements for the balance, APR, payment due information, and any rate or fee terms needed to build that schedule. This calculation is educational arithmetic, not financial advice.

Frequently Asked Questions

How long will it take to pay off my credit card?
Enter the balance, APR, and monthly payment to estimate the number of months. The result assumes the APR and payment remain fixed and no new charges or fees are added.

Why does the calculator say it cannot compute my payoff time?
The payment may be zero or too small to cover the interest accruing in a month. A payment must exceed the monthly interest for the balance to decline under this formula.

Does the estimate include new purchases or fees?
No. It assumes the balance only declines through the entered payments and does not include new purchases, fees, or other account adjustments.

Is APR the same as the monthly interest rate?
No. APR is an annual percentage rate. This estimate converts it to a monthly rate by dividing the percentage by 12, or by 1,200 when using the numeric percentage entered in the calculator.

Why might my statement show a different payoff amount?
Account interest may be calculated from daily balances, and the payment date, final payment size, fees, rate changes, or new transactions may differ from the calculator’s assumptions.

The result is an estimate; the lender’s disclosure and account terms give the exact figures.

Related

• Amortization Schedule Spreadsheet: Payment and Interest
• Amortization Schedule by Month: Payment and Interest
• Amortization Schedule Software: Payments and Interest

in bal | Credit card balance | $ | 5000 | 0.01 | 100000000
in apr | Interest rate (APR) | % | 20 | 0.01 | 100
in pay | Monthly payment | $ | 250 | 0.01 | 100000000
out mos | Estimated months to repay | months | ceil(round(-ln(1 - (apr / 1200) * bal / pay) / ln(1 + apr / 1200), 6)) | 0
out tot | Total of payments | $ | mos * pay | 2
out int | Estimated interest | $ | mos * pay - bal | 2