Credit Card Payoff Calculator: Time, Payment and Interest

A credit card payoff calculator estimates how many months it will take to clear a balance, the monthly payment needed by a target date, and the interest paid along the way. Enter your balance, APR, and either your planned monthly payment or payoff period to estimate the result.

Formula

The calculator estimates the number of level monthly payments needed to repay a balance while interest accrues monthly. It uses:

r = APR / 1200
n = ceil(round(−ln(1 − r × B / P) / 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.
• P is the monthly payment in dollars.
• n is the estimated number of monthly payments, rounded up to a whole month.

Total paid is estimated as P × n, and estimated interest is total paid minus the starting balance. This assumes the same payment is made each month, including the final month. Since a real final payment may be smaller, the total and interest can be slightly overstated. The calculation also assumes interest is applied to the balance at a steady monthly rate; card issuers may calculate interest using daily balances and specific billing-cycle rules.

Worked Example

Using the calculator defaults, the balance is $5,000, APR is 20%, and the monthly payment is $200.

1. Convert APR to a monthly decimal rate: r = 20 / 1200 = 0.0166667.
2. Substitute into the payoff formula: n = ceil(−ln(1 − 0.0166667 × 5,000 / 200) / ln(1.0166667).
3. Calculate the fraction inside the logarithm: 1 − 0.0166667 × 25 = 0.583333. The unrounded payment count is about 34.0 months, so the estimate is 34 months.
4. Total paid estimate: $200 × 34 = $6,800.00.
5. Estimated interest: $6,800.00 − $5,000.00 = $1,800.00.

The amount of interest is an estimate: the calculation counts 34 full payments of $200, although a real account may be cleared with a smaller final payment. The formula’s result should be treated as a planning approximation, not a billing statement.

Assumptions

• The APR stays fixed for the full payoff period.
• Payments are made once per month, with no missed or late payments.
• Interest compounds monthly at APR divided by 12.
• No new purchases, cash advances, balance transfers, fees, or payment-allocation effects are included.
• The estimated total assumes the same payment every month; the actual final payment can be lower.

How to Use the Calculator

Enter the balance you want to pay off, the APR that applies to that balance, and the amount you expect to pay each month. Use the APR shown for the relevant balance on your card statement or account information. If different portions of your balance have different rates, such as purchases and a promotional transfer, this single-rate calculation cannot model them separately.

The main result is the estimated payoff time in whole months. The other results estimate total payments and the interest component. A payment must be greater than the interest added in a month for the balance to decline. For example, at a monthly rate of 1.6667%, a $5,000 balance accrues roughly $83.33 in one month under this simplified model. A payment of $83.33 or less would not reduce the balance; the calculator cannot return a finite payoff time for such an input.

To interpret months as a calendar estimate, count forward from the next payment cycle. The result is not an exact due date: statement dates, payment posting, changes to the APR, and daily balance calculations can shift the outcome. The calculator’s monthly interest approximation is useful for understanding the relationship between balance, rate, and payment, but your issuer’s account calculation is authoritative for the amount due.

Reading the Result and Common Mistakes

• Entering a minimum payment as a fixed amount: Many minimum-payment amounts change as the balance changes. If your payment will vary, this fixed-payment estimate may not match the actual payoff schedule.
• Using a monthly rate as the APR: Enter the annual percentage rate, not the monthly rate. The calculator divides APR by 1,200 to obtain a monthly decimal rate.
• Ignoring new transactions: New charges add to the amount owed and may accrue interest under different terms. The calculation assumes no new activity.
• Assuming the final payment is exact: The whole-month estimate rounds up. A real account is generally cleared by paying the remaining amount, not necessarily another full planned payment.
• Mixing balances with different rates: A single APR cannot represent multiple rate buckets or how payments are allocated across them.

Small differences in rounding can matter over many months. The formula rounds the computed month estimate to six decimal places before rounding up to a whole month; displayed dollar totals are rounded to cents. Actual statements may use more detailed daily calculations.

When This Estimate Is Useful—and Its Limits

A payoff calculator can help compare hypothetical combinations of balance, APR, and fixed monthly payment. For instance, you can change the payment input to see how a different assumed payment changes the estimated duration. These are mathematical scenarios, not predictions about an account’s future terms.

The model does not determine a required minimum payment, account fees, promotional-rate expiration, penalty APR, or the order in which payments are applied. It also does not account for a changing APR or changes in spending. For a more exact account-specific figure, check the card’s current terms and statement, and ask the issuer how it calculates interest and payments.

Frequently Asked Questions

How long will it take to pay off my credit card?
It depends on your balance, APR, and monthly payment. Enter those values above for an estimate. If your payment does not exceed the interest accruing each month, the balance will not be paid off under this model.

Does the calculator include credit card interest?
Yes. It estimates interest using a fixed APR converted to a monthly rate. It does not reproduce an issuer’s exact daily balance method, so its interest estimate can differ from a statement.

Why does my credit card payoff estimate differ from my statement?
The calculator assumes a fixed monthly payment and rate, monthly compounding, and no new transactions or fees. Issuers may use daily balances, billing-cycle dates, changing rates, and other account-specific details.

Can I enter a payment that changes every month?
Not in this fixed-payment calculator. Entering one amount gives an estimate as if that payment were repeated each month. A changing payment schedule requires calculating each month’s interest and remaining balance separately.

What if I have balances at different APRs?
This calculator treats the full balance as if it has one APR. For separate purchase, transfer, or cash-advance balances, estimate each balance separately only as a rough illustration; payment allocation and account terms can affect the actual result.

This result is an estimate, and your card issuer’s disclosure and account records provide 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 pay | Monthly payment | $ | 200 | 0.01 | 100000000
out mon | Months to pay off | months | ceil(round(-ln(1 - (apr / 1200) * bal / pay) / ln(1 + apr / 1200), 6)) | 0
out tot | Total paid | $ | pay * mon | 2
out int | Total interest | $ | pay * mon - bal | 2