Credit card calculators
Five calculators for the questions a statement does not answer: how long a balance takes to clear, what it costs per day, what the minimum payment really buys you, and whether a bank bonus is worth the cash it locks up, before and after tax. The interest calculator and the bank bonus calculators run on this page. Payoff and minimum-payment examples open in the CardLab simulator with the numbers filled in.
These tools live on the CardLab home site, next to the billing-cycle guide and the iPhone app. After you run a balance, keep the statement dates and due dates in the credit card tracker. A checking or savings offer belongs on the bank bonus tracker, then in the bank bonus ROI calculator.
What each calculator answers
Each tool is one question. Pick the question you actually have; the cards below open that page with a worked example.
- Payoff calculator: months and interest to clear a balance at a fixed payment versus the minimum.
- Interest calculator: payoff months and total interest from a balance, an APR and a monthly payment, plus the daily cost while you carry it. A grace period on a credit card can make that purchase interest zero.
- Minimum payment calculator: what the issuer-style minimum is, and when it stops reducing the balance.
- Bank bonus ROI calculator: what a sign-up bonus returns on the cash it makes you park. The method is in is a bank bonus worth it.
- Bank bonus tax calculator: what that cash bonus leaves after ordinary income tax. See also do you pay taxes on bank bonuses.
Why these are not the usual calculator widget
Most payoff calculators divide a balance by a payment and call it a day. CardLab runs the average daily balance method, applies the greater-of minimum payment rule, and tells you when the minimum has stopped reducing your balance at all instead of printing a payoff date that will never arrive. See how average daily balance interest works for the day-by-day version of that method. The numbers on these pages come from the same engine as the app rather than from a separate script written for the website.
The same standard applies to card data. CardLab publishes 673 cards from 149 issuers across 38 markets, and 1,507 of its 1,507 rate and annual-fee claims carry the issuer page they were read from, the sentence on that page, and the date they were read. Claims verified between 2026-09-24 and 2026-09-28. See coverage by market.
When to track first
A calculator answers one balance. If you hold more than one card, the dates and caps belong in the credit card tracker first, then you run the math on those numbers.
- The statement date of each card, which is usually when utilization is reported.
- The due date, and whether paying the statement balance in full keeps the grace period.
- How much of each limit is used on the statement date, not only on the due date.
- How much room is left under each bonus rate before the cap flips the ranking.
The date split is statement date versus the due date. Paying in full is what keeps a grace period on a credit card. The snapshot itself is what credit utilization gets reported.
Modeling an ATM-like pull first? Read cash advance before you run the numbers. Bonus ROI and tax tools pair with the bank bonus guides.
Related guides and tools
Common questions
What can a credit card calculator tell you?
A payoff calculator turns a balance, an APR and a payment into months and interest. An interest calculator shows the daily cost of carrying that balance. A minimum payment calculator shows what the issuer-style minimum actually buys you. The two bank bonus calculators answer a different question: what a sign-up bonus returns on parked cash, and what tax leaves.
Do I need to sign up to use these calculators?
No. The interest calculator and the bank bonus calculators run on this page. The payoff and minimum-payment examples open the CardLab simulator in the browser with the example numbers filled in. Nothing is stored on a server.
Should I track my cards before I run a calculator?
If you hold more than one card, yes. Statement dates, due dates and remaining reward caps belong in the credit card tracker. The calculators then run on those balances instead of on a guess.
Are these the same numbers as the CardLab iPhone app?
Yes. The published figures come from the same engine the app runs, not from a second script written for the website. Change any input and the cycle recalculates the same way.