Credit Card Debt Payoff Calculator

A credit card debt payoff calculator estimates how many months it may take to repay a balance and how much interest you may pay, based on your balance, APR, and monthly payment. Enter those figures to see an estimated payoff time and total paid; it assumes a fixed rate and an unchanged payment.

Formula

The calculation treats the card balance as a fixed-rate debt with interest added monthly. It estimates the number of equal monthly payments needed to reduce the balance to zero:

n = ceil(round(−ln(1 − rB / M) / ln(1 + r), 6))

• B is the starting balance in dollars.
• A is the annual percentage rate (APR), entered as a percentage.
• r is the monthly rate as a decimal: A ÷ 1,200.
• M is the monthly payment in dollars.
• n is the estimated number of monthly payments, rounded up to a whole month.

The calculator then estimates total paid as M × n, and interest as (M × n) − B. The extra validity check in the month expression prevents a result when the payment does not exceed the first month’s interest. If the payment is zero or too small to cover interest, the payoff period cannot be calculated.

Worked Example

Using the calculator’s defaults: balance B = $5,000, APR A = 20%, and monthly payment M = $200.

1. Convert the APR to a monthly decimal rate: r = 20 ÷ 1,200 = 0.0166667.
2. Calculate the first month’s interest: $5,000 × 0.0166667 ≈ $83.33. The $200 payment exceeds that amount.
3. Apply the payoff formula: n = ceil(round(−ln(1 − (0.0166667 × 5,000 ÷ 200)) ÷ ln(1.0166667), 6)) = ceil(35.07) = 36 months.
4. Total paid = 36 × $200 = $7,200.00.
5. Estimated interest = $7,200 − $5,000 = $2,200.00.

These are estimates from the stated formula, not a card issuer’s billing schedule. In the final month, an actual payment may be less than the regular amount because only the remaining balance and accrued interest are due.

Assumptions

• The APR remains fixed for the entire payoff period.
• A payment is made once per month at the end of each monthly interest period.
• Interest compounds monthly at APR ÷ 12, with no daily-balance variation modeled.
• The monthly payment stays the same, including in the final month for the estimate.
• Fees, new purchases, cash advances, promotional rates, penalties, taxes, and changes to the account terms are not included.

How to Use the Estimate

Use the current balance shown on your account and the APR that applies to that balance. If purchases, transfers, and cash advances have separate rates, a single APR cannot represent them precisely; calculate each balance separately or use an account statement’s relevant rate. Enter the amount you expect to pay each month, not the minimum payment unless that is the payment you want to model.

The result is most useful as a planning illustration: compare the estimated time and interest under different payment amounts, while keeping the balance and APR the same. A larger fixed payment generally shortens the modeled payoff time, provided it covers interest. This does not establish what payment is appropriate for your circumstances.

• Months to repay: a whole-month estimate, rounded up. For instance, 36 means the model requires 36 monthly payments of the entered amount.
• Total paid: the payment multiplied by the estimated number of months. It may overstate the final payment because the model does not reduce that last payment.
• Total interest: estimated total payments minus the starting balance. It is not a separate fee or amount guaranteed by the card issuer.

What Can Change the Result?

Credit card interest is often calculated using daily balances and a daily periodic rate, so the exact charge can depend on the issuer’s method, transaction timing, and when payments post. This calculator simplifies that process to monthly compounding. The difference may become more noticeable over a long payoff period or when the balance changes frequently.

New purchases, late or returned payments, fees, rate changes, and different rates for separate transaction categories can all alter the actual balance. A minimum payment may also change from month to month under the account’s terms. The calculator models none of those events; it assumes one balance, one unchanging APR, and a steady payment.

A common misconception is that paying more than the minimum automatically means the balance will be gone in the number of months shown. That is true only if the assumptions hold and the payment is actually applied as modeled. Check your statement and account terms for the actual balance, interest method, applicable rates, and payment allocation.

Common Input Problems and Alternatives

• Payment is at or below monthly interest: the calculator cannot produce a payoff period because the balance would not decline under its assumptions. For the default $5,000 balance at 20% APR, first-month interest is about $83.33.
• APR entered incorrectly: enter 20 for 20%, not 0.20. The formula converts the percentage to a monthly decimal rate.
• Balance is not current: a recent charge or payment can make a past statement balance inaccurate for a new estimate.
• Multiple balances: separate APRs or payment-allocation rules mean a single-balance estimate is incomplete. A detailed spreadsheet or issuer-provided payoff tool may model those factors more closely.

If you need exact account-specific figures, review your latest statement or contact the card issuer. A nonprofit credit counselor may explain general debt-management options, but this calculator does not evaluate a particular service or plan.

Frequently Asked Questions

How do I calculate how long it will take to pay off credit card debt?
Use the balance, APR, and a fixed monthly payment in the payoff formula. The payment must be greater than the interest charged in a month; otherwise, the balance will not be repaid under this model.

Does this calculator use the minimum payment?
No. Enter the monthly amount you want to model. Minimum-payment formulas vary by account and can change over time, so check your statement for your required payment.

Why does the calculator say it cannot compute?
The payment may be zero or no greater than the estimated first month’s interest. At that payment level, this fixed-payment model cannot reach a payoff date.

Is the interest amount exact?
No. It is an estimate based on monthly compounding, a fixed APR, and equal payments. Your issuer’s daily-balance method, payment dates, fees, and new transactions can change the actual amount.

What if my card has more than one APR?
One calculation cannot accurately model several balances with different rates. Treat each balance separately for a rough illustration, and consult your statement for how payments are allocated.

This result is an estimate, and the card issuer’s disclosure and account terms give the exact figures.

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