Credit Card Debt Repayment Calculator: Payoff Time and Cost

A credit card debt repayment calculator estimates how many months it will take to pay off a balance with a fixed monthly payment, and the total interest paid along the way. Enter your balance, APR, and monthly payment to see the estimated payoff time, interest, and total amount paid.

Formula

The calculator uses a fixed monthly interest rate and assumes the same payment is made once per month. It first estimates the number of months needed to clear the balance, rounding up to a whole month:

r = APR / 1200
n = ceil(round(−ln(1 − r × B / M) / ln(1 + r), 6))

• B is the starting balance, in dollars.
• APR is the annual percentage rate entered as a percentage, such as 20 for 20%.
• r is the monthly rate as a decimal.
• M is the monthly payment, in dollars.
• n is the estimated number of monthly payments.

It then calculates total paid = M × n and total interest = total paid − B. These totals use the entered payment for every month, including the final month. Actual card payments commonly stop at the amount needed to clear the remaining balance, so the calculator’s total can overstate the final payment and total cost slightly. It is an estimate rather than a statement-level payoff calculation.

Worked Example

Using the calculator’s default inputs—balance $5,000, APR 20%, and monthly payment $200—the monthly rate is:

r = 20 / 1200 = 0.0166667, or about 1.6667% per month.

Substitute those values into the payoff formula:

n = ceil(round(−ln(1 − 0.0166667 × 5000 / 200) / ln(1.0166667), 6))
n = ceil(32.578…) = 33 months

The estimated total paid is $200 × 33 = $6,600.00. The estimated interest is $6,600.00 − $5,000.00 = $1,600.00. Because the calculation counts 33 full payments, the last payment in practice may be smaller than $200.

Assumptions

• The APR stays fixed for the entire payoff period.
• A payment is made once per month, with interest accruing at the monthly rate APR / 12.
• The calculation treats the balance as accruing monthly interest and does not model daily balance methods or payment dates.
• No new purchases, cash advances, late charges, annual fees, promotional-rate changes, or other fees are added.

When to Use a Payoff Calculator

Use this estimate to understand how a payment amount relates to payoff time and interest under simplified, steady conditions. You can compare scenarios by changing the monthly payment or APR and noting how the output changes. For example, a larger fixed payment generally reduces the time spent carrying a balance and the interest accumulated, provided it exceeds the interest charged each month.

The result can help turn a balance into a rough timeline, but it is not a payment instruction or a forecast of a particular account. If your balance includes different purchase categories or promotional offers, one APR may not describe the whole account. Check your card statement and account terms for the applicable balance, APRs, fees, and payment allocation details.

How to Read the Results

Months to repay is rounded up because a balance is not considered paid off until the final payment clears it. Total paid multiplies your stated payment by that whole number of months. Total interest is the estimated amount above the starting balance under this simplified calculation.

The model requires a payment large enough to cover interest. At the defaults, one month of interest on $5,000 is approximately $83.33. A payment at or below the interest charge does not reduce the balance, so there is no finite payoff estimate. The calculator may display “Cannot compute” in that situation. A payment only slightly above monthly interest can also produce a very long payoff period.

Common Sources of Difference

• Variable APR: A rate change during repayment changes the interest calculation and payoff time.
• Daily interest calculations: Many card accounts calculate interest using daily balances. The amount depends on when transactions and payments post, which this monthly model does not represent.
• New charges or fees: Additional spending, cash advances, or charges increase the balance and may have different rates.
• Payment changes: Paying a different amount each month means the fixed-payment formula no longer applies.
• Rounding: The calculator rounds payoff time to a whole month and does not separately calculate a smaller final payment. Statement totals may therefore differ.

A common misconception is that paying a fixed amount guarantees the displayed payoff date. It does not: the estimate depends on the inputs and assumptions remaining accurate. Use the current balance and APR from your account information, and update the estimate if either changes.

Frequently Asked Questions

How much should I pay each month to pay off a credit card?
This calculator estimates the payoff time for a payment amount you enter; it does not prescribe a payment. To calculate a target payment for a chosen deadline, use a calculator designed for that specific question and account for the APR and fees shown by the issuer.

Why does the calculator say it cannot compute?
The entered payment may not exceed the interest estimated for the first month. If a payment does not cover interest, the balance will not decline under this model, so a finite payoff time cannot be calculated.

Does the calculator include new purchases?
No. It assumes no new charges, fees, or balance transfers. Additions to the account change the balance and may be subject to different APRs.

Why is my card’s payoff estimate different?
Your account may use daily balance calculations, a variable APR, multiple rates, fees, or changing payment amounts. The estimate also assumes a full payment in the final month, while the actual payoff amount may be lower.

Is credit card APR the same as the monthly interest rate?
No. APR is an annual percentage rate. This calculator divides APR by 12 to estimate a monthly rate; the account’s actual interest calculation may use daily balances and other terms.

This result is an estimate for educational purposes, and the lender’s disclosure gives the exact figures.

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in bal | Credit card balance | $ | 5000 | 0.01 | 100000000
in apr | Interest rate (APR) | % | 20 | 0.01 | 100
in pmt | Monthly payment | $ | 200 | 0.01 | 100000000
out mon | Months to repay | months | ceil(round(-ln(1 - (apr / 1200) * bal / pmt) / ln(1 + apr / 1200), 6)) | 0
out tot | Total paid | $ | pmt * mon | 2
out int | Total interest | $ | pmt * mon - bal | 2