Credit card payoff calculator: see months to debt freedom and total interest saved at any monthly payment amount you choose. Free, editable rates, no signup.
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Credit card payoff calculator: see months to debt freedom and total interest saved at any monthly payment amount you choose. Free, editable rates, no signup.
At $150 a month, $3,000 at 21% APR costs $724.82 in interest
Transparent methodology
How this calculator works
Formula
Each month, interest equals the current balance × APR ÷ 12. The payment is then subtracted, and the process repeats until the balance reaches zero.
Worked example
With an $8,000 balance, 22% APR, and a $300 monthly payment, the calculator iterates month by month to estimate payoff time, total interest, and total paid.
This calculator running on this page with the inputs above — produced locally, not a mock-up.
BoringToolsKit. “Credit Card Payoff Calculator.” boringtoolskit.com/credit-card-payoff-calculator/. Free to reference in articles, syllabi, and answer posts with a link.
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A worked example: $3,000 at 21% APR
Take a $3,000 balance at 21% APR, paying $150 a month. The monthly rate is 21% divided by 12, or 1.75%. Month one: interest is $3,000 x 0.0175 = $52.50, so the balance grows to $3,052.50, then your $150 payment drops it to $2,902.50. Month two: interest is $2,902.50 x 0.0175 = $50.79, balance after payment $2,803.29. Month three: interest $49.06, balance $2,702.35.
Run the loop to zero: 25 months, $724.82 in interest, $3,724.82 total paid. Now raise the payment to $200 and the same debt clears in 18 months costing $510.67 in interest. At $300 a month it is 12 months and $326.79. The extra $50 a month between $150 and $200 buys back 7 months and $214 of interest; the next $50 buys 6 months and $184 more. Each dollar of extra payment saves less than the last, which is why early increases matter most.
One guard rail worth knowing: your payment must beat the first month's interest. At $3,000 and 21% that floor is $52.50, so a $50 payment never repays the debt and the calculator stops with an error rather than showing an infinite payoff.
Where the flat-payment model diverges from real cards
The calculator assumes you pay one fixed amount until the balance hits zero. Most card issuers instead compute a minimum payment as a percentage of the current balance, typically the greater of 1% to 3% of the balance plus that month's interest, or a floor like $25 to $35. That structure front-loads large payments and shrinks them as the balance falls, which stretches payoff by years: a $3,000 balance on a 2%-of-balance-plus-interest minimum can take well over 10 years to clear, versus 25 months at a flat $150.
It also assumes a constant APR. Promotional 0% intro rates expiring, a penalty rate triggered by a late payment, or a prime-rate-linked variable APR all change the monthly rate mid-payoff, and none of that is modeled. Cash advances often accrue interest from day one at a higher rate than purchases, so a balance mixing the two is priced at one blended rate here.
Finally, timing is simplified. The model charges interest on the full starting balance each month, while real cards use daily periodic interest (APR divided by 365) on the average daily balance, adjusted for your grace period. The difference is usually small, a few dollars on a $3,000 balance, but it grows with the balance size.
