Credit Card Payoff Calculator: Estimate Time and Interest

A credit card payoff calculator estimates how many months it may take to clear a balance with a fixed monthly payment, and how much interest that payment schedule adds. Enter your current balance, APR, and planned monthly payment to see an estimated payoff time and total interest.

Formula

The calculator estimates the number of level monthly payments needed to repay a balance with a fixed APR, then subtracts the starting balance from the sum of those payments to estimate interest paid.

• B = current balance, in dollars.
• a = annual percentage rate (APR), entered as a percentage per year.
• r = monthly rate, calculated as a / 1200.
• M = planned monthly payment, in dollars.
• N = estimated months, calculated as ceil(round(-ln(1 – rB/M) / ln(1 + r), 6)).
• I = estimated total interest, calculated as M × N − B.

The months formula comes from the balance equation for a fixed payment: the balance after N payments is B(1 + r)^N − M × ((1 + r)^N − 1) / r. Setting that balance to zero and solving for N gives the logarithm formula. Rounding the calculated time upward represents the next whole monthly payment. This simplified model assumes the same payment amount each month.

Worked Example

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

1. Convert APR to a monthly rate: r = 20 / 1200 = 0.0166667, or about 1.66667% per month.
2. Find the unrounded payoff time: -ln(1 − (0.0166667 × 5,000 / 250)) / ln(1 + 0.0166667) ≈ 25.07 months.
3. Round up to a whole payment period: N = 26 months.
4. Estimate total payments: $250 × 26 = $6,500.
5. Subtract the original balance: estimated interest I = $6,500 − $5,000 = $1,500.

The calculator’s headline result is 26 months, with estimated total interest of $1,500. Actual card statements may show a different final payment because issuers generally calculate interest and minimum payments using account-specific terms and daily activity.

Assumptions

• The APR stays fixed throughout the estimated payoff period.
• A payment is made once per month, with the calculation treating payments as level monthly amounts.
• Interest compounds monthly at APR / 12.
• No new purchases, late payments, payment changes, annual fees, or other charges are included.
• The calculation does not model taxes, insurance, or escrow; those do not normally form part of this credit-card payoff estimate.

When to Use the Calculator

Use it to understand how a proposed fixed payment relates to payoff time and estimated interest. You can adjust the payment amount to see how the estimate changes. It can also help compare hypothetical payment schedules for the same starting balance and APR, provided you treat the outputs as arithmetic estimates rather than account-specific promises.

For a useful estimate, enter the current balance and APR shown on your latest statement or account disclosure. If the card has more than one balance category, such as purchases and cash advances, those amounts may have different rates. A single-balance calculator cannot represent that accurately; calculate each category separately only if the payment allocation rules and rates are known, or use a tool that models the account’s categories.

How to Read the Results

The months result is a whole-number estimate, not a calendar payoff date. Twenty-six months means the model needs 26 monthly payment periods. The interest result is the modeled amount above the starting balance, based on making the entered payment for every period, including the last one.

There is an important limitation in this simple estimate: it counts every payment as the same amount, including the final payment. In real repayment, the remaining balance may be smaller than the regular payment, so the last payment is often reduced. The estimated total interest can therefore be higher than an exact schedule would show. In addition, the formula treats interest as monthly compounding, while a card issuer may calculate interest daily and use a particular statement-cycle method.

Common Problems and Alternatives

If your monthly payment does not exceed the first month’s modeled interest, the calculator cannot produce a finite payoff time. Here, that condition is M ≤ rB: with the default balance and APR, the first month’s interest is about $83.33, so a payment at or below that amount would not reduce principal under this model. The required payment in practice can also be affected by the card’s minimum-payment terms.

• Payment amount changes: A fixed-payment estimate will not match a schedule where you pay different amounts month to month.
• New charges or fees: Purchases, fees, or missed payments can increase the balance and extend payoff time.
• Changing APR: A variable rate or promotional period ending during repayment makes the fixed-rate assumption inaccurate.
• Rounding: The formula rounds payoff duration up to a whole month. Statement interest is usually calculated to finer precision and can vary by a small amount.

For a more detailed estimate, use the card’s balance, rate, payment timing, and payment-allocation details in an amortization schedule that can model daily interest, different balance categories, and a smaller final payment. For the exact amount due or account-specific payoff information, consult the issuer’s current statement or account disclosure.

Frequently Asked Questions

How do I calculate how long it will take to pay off a credit card?
Convert the APR to a monthly rate, apply the fixed-payment payoff formula, and round the resulting number of months up. This calculator performs that estimate from the balance, APR, and monthly payment.

Why can’t the calculator calculate my payoff time?
The entered payment may be no greater than the modeled monthly interest on the balance. A payment must exceed the interest charge for the balance to decline under this fixed-rate model.

Does the estimate include new purchases?
No. It assumes no additional charges. Purchases and fees added during repayment can raise the balance and change both payoff time and interest.

Is the total interest exact?
No. It is an estimate based on monthly compounding and equal payments, including a full regular payment in the final month. The account’s daily interest method, payment dates, fees, and final payment can produce different figures.

What APR should I enter?
Use the APR applicable to the balance you are estimating, as shown in the current account information. If separate balance categories have different APRs, this one-rate calculator does not combine them.

The result is an estimate; 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 | $ | 250 | 0.01 | 100000000
out mos | Months to repay | months | ceil(round(-ln(1 - (apr / 1200) * bal / pmt) / ln(1 + apr / 1200), 6)) | 0
out int | Estimated total interest | $ | pmt * mos - bal | 2