What this calculator does
This tool shows the true cost of paying the minimum on one or more credit cards. Add each card's balance, APR, and minimum payment terms, then compare the combined payoff timeline with and without a one-time extra purchase, like an impulse buy or emergency expense.
The math
Minimum payment = max(balance × minimum %, floor amount). Each month interest = balance × APR ÷ 12. The tool loops payments until every card balance hits zero and totals combined months, interest, and the added cost of the extra purchase.
Worked example
With one card at $3,000, 24.99% APR, 3% minimum payment, and a $25 floor, the minimum payment starts around $90. Adding a $500 impulse purchase to that card stretches the combined payoff and adds hundreds in extra interest.
Why this matters
Most people underestimate the cost of small interest and fee decisions. This calculator turns the hidden math into a number you can act on today.
Methodology and transparency
This page publishes the exact formula used to compute the result, so you can verify it in a spreadsheet or check the assumptions against your own situation. The worked example uses the tool default inputs; change any number and the result updates live in your browser. No data is sent or stored.
Common questions
How is the minimum payment calculated?
It is the larger of the balance times your minimum percentage or the floor amount, usually $25–$35.
Why does minimum payment take so long?
Because most of the payment goes to interest, so the principal shrinks slowly and the term stretches for years.
How much does one extra purchase add in interest?
The calculator shows the extra months and combined interest caused by adding a one-time extra purchase to one card and paying only the minimum across all cards.
What counts as an extra purchase?
Any one-time charge you add to one of your balances: an impulse buy, a vacation, a car repair, or another unplanned expense.
Should I pay more than the minimum?
Yes. Even an extra $25–$50 per month can cut months or years off the payoff and save hundreds in interest.
Can I add more than one card?
Yes. Click Add Another Card to enter as many cards as you need. The calculator totals the combined balance, months, and interest.