Credit Card Interest Calculator — What Carrying a Balance Costs
Monthly interest on a carried balance, payoff time at your payment, and the daily-compounding truth behind the APR.
Formula
Disclaimer: Indicative math — lenders differ on day-count, rounding, fees and how extra payments are applied. Confirm with your servicer; this is not financial advice.
Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.
Need credit card interest calculator results fast? Skip the spreadsheet and get a clear, defensible answer in one step — free, private and instant, recalculating live as you change any input.
About Credit Card Interest Calculator — What Carrying a Balance Costs
Credit-card interest is the most expensive mainstream money there is, and it compounds DAILY: a $5,000 balance at 24% APR accrues about $3.29 every single day — roughly $100 a month before your payment touches a dollar of principal. The daily figure is this calculator's psychological payload: a balance has a metered cost per sunrise, and naming it changes spending behavior more than the abstract APR ever did. The grace period is the system's misunderstood hinge: while you pay the FULL statement balance by the due date, purchases accrue no interest at all — the card is free money for up to ~55 days. Carry even $1 past the due date and most issuers revoke the grace period entirely: new purchases start accruing from the day of swipe, and 'residual interest' appears on statements people thought they'd paid off. The cliff between full-payment and carry-a-balance behavior is binary, which is why the only two stable strategies are 'always in full' or 'aggressive payoff plan'. At the default numbers, $200 a month kills the $5,000 balance in about 36 months at ~$2,000 of interest — while the minimum-payment path (interest + 1% of balance) takes well over a decade and costs more than the original balance. If the balance is real, the escape routes in order of power: a 0% balance-transfer card (12–21 months of frozen interest for a 3–5% fee), a personal loan at a third of the APR, and the avalanche method across multiple cards. All three beat raw willpower at 24%.
How to use Credit Card Interest Calculator — What Carrying a Balance Costs
- 1Enter Carried balance, Purchase APR (%), Monthly payment into the Credit Card Interest Calculator.
- 2The result is computed automatically using Card interest accrues DAILY: balance × (APR ÷ 365), compounding — a 24% APR is ~26.8% effective; the grace period only exists while you pay in full — there is no button to press; it updates live as you type.
- 3Change any input to model a different scenario, then use “Copy result link” to share the exact numbers.
Why use Credit Card Interest Calculator — What Carrying a Balance Costs?
- ✓Computes credit card interest calculator instantly with the correct formula — no spreadsheet needed
- ✓100% free and unlimited, with no sign-up, login or paywall
- ✓Runs entirely in your browser, so the figures you enter are never uploaded or stored
- ✓Shows the formula, a live worked example and references so you can defend the number
Frequently asked questions
Why was I charged interest after paying the full balance?+
Residual (trailing) interest: between the statement date and the day your payment landed, the OLD balance kept accruing daily interest, which appears on the NEXT statement. It bites people exiting a carried balance — pay the 'payoff amount' (call the issuer or check the app for the real-time figure), not the last statement balance, and the following month shows zero. One more full-statement payment after that restores the grace period.
How is my monthly interest actually computed?+
Most US issuers use average daily balance with daily compounding: each day's balance × (APR ÷ 365), summed across the cycle — so a mid-cycle payment cuts interest immediately, and a big purchase early in the cycle costs more than the same purchase late. This calculator's 30.44-day month on the input balance lands within cents of statement math; the practical lever is paying as early in the cycle as you can, not just by the due date.
Is a balance transfer actually worth the 3–5% fee?+
Almost always when you'd otherwise carry months at 20%+: moving $5,000 for a 3% fee ($150) onto an 18-month 0% card saves most of the ~$2,000 of interest the default scenario burns — over 12× the fee. Two conditions make it work: a written payoff plan that clears the balance INSIDE the promo window (divide balance by months and automate it), and not spending on the old card. Miss the window and deferred-interest products can claw back everything.
Do cards in India / UK work the same way?+
Mechanics yes, numbers worse in India: card APRs run 36–48% annually (3–4% per MONTH), grace periods work the same and the revolving trap is identical — and minimum payments (5% in India) stretch payoff into decades. UK cards (~25–35% APR) add a persistent-debt rule forcing issuers to escalate contact after 18 months of interest-exceeding-principal. Whatever the country: this calculator's daily-cost line, at your APR, is the universal translator.
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