A $3,000 credit-card balance at 26.99% APR sounds abstract until it is priced: about $66.55 of interest in the first month, $756.12 over a year of minimum payments — and after paying $1,096.96, you would still owe $2,659.15. This guide works the arithmetic out in full: how card interest is charged by the day, what the minimum-payment path really costs, how the same balance behaves at 20% and 30% APR, and why a cash advance is the most expensive money on the card.

The daily periodic rate: how card interest is actually charged

Credit cards do not charge interest the way loans do. Most issuers use the daily periodic rate method — the common method, and the one used throughout this guide. The APR is divided by 365 to get a daily rate: at 26.99% APR that is 0.07395% per day. Each day’s rate is applied to your average daily balance for the billing cycle, so a balance carried for more days, or a bigger balance mid-cycle, costs more than the headline APR might suggest.

Two features of card interest follow from this. First, there is a grace period on purchases: pay the statement balance in full by the due date and no purchase interest is charged at all. The APR only starts costing money when a balance is carried past that date — and once it is carried, interest generally accrues from the transaction dates, not from the due date. Second, a card APR contains no fee solve. Unlike a loan APR, which rises above the note rate when fees are added, a card’s APR is simply the periodic rate annualised; annual fees are disclosed separately under Regulation Z and are never folded into it. That is why a card’s APR and its purchase interest rate are normally the same number.

How much is 26.99 APR on $3,000?

Hold a $3,000 balance steady for a 30-day month and the arithmetic is direct: $3,000 × 0.07395% × 30 days = $66.55 of interest. A 31-day month costs $68.77. The monthly periodic rate you may see on a statement is the same figure in monthly dress — 26.99% ÷ 12 = 2.2492% — which gives the same neighbourhood: about two and a quarter percent of the balance, every month, for as long as the balance stands.

Stretch that to a year. If the balance stayed at $3,000 for twelve months — new spending exactly replacing what you pay toward principal — the interest would be $3,000 × 26.99% = $809.70. Nobody’s balance is that tidy, but the figure is the honest scale of the thing: a carried $3,000 balance at this rate costs roughly $810 a year before it shrinks by a cent.

Paying only the minimum: the twelve-month ledger

Most issuers set the minimum payment as the month’s interest plus 1% of the balance — a common formula, used here so the path can be worked exactly. On $3,000 at 26.99% APR:

Minimum payment modelled as interest plus 1% of the balance each month, interest by the daily periodic rate over 30-day months — stated assumptions, every figure recomputed.

Read the last row slowly: $1,096.96 paid, of which $756.12 was interest, and the balance fell by just $340.85. The minimum payment is engineered to shrink the balance by 1% a month, which means it is engineered to keep you paying interest for a long time. Doubling the payment is what changes the story — every extra dollar goes entirely to principal, because the interest for the month is already fixed by the balance you carried.

The same $3,000 at 20% APR and 30% APR

Rate differences that look small in a headline are large in a ledger. The same $3,000 balance, three rates:

Same balance and same minimum-payment formula throughout; only the APR changes.

The spread between a 20% apr card and a 30% apr card is $280.15 of interest over a single year of minimum payments on one $3,000 balance — which is why the rate deserves more attention than the rewards programme when a balance will be carried.

Paying more than the minimum: what actually changes

The minimum payment’s flaw is that it is a percentage — as the balance falls, so does the payment, and the loan from yourself stretches out. A fixed payment breaks the pattern, because the interest shrinks every month while the payment does not, so the principal portion grows on its own. On the same $3,000 at 26.99% APR, by the same daily-rate method: a fixed $150 a month clears the balance in 27 months at a total interest cost of $1,009.22. Even a fixed $100 a month — barely above the first minimum payment of $96.55 — clears it in 50 months for $1,991.36. Compare the minimum path, which after a full year of payments still leaves $2,659.15 outstanding and has years left to run. The lesson is not that $150 is magic; it is that fixing the payment, at almost any level you can sustain, converts an open-ended interest bill into a schedule with an end date — and every extra dollar goes to principal, because the month’s interest is already determined by the balance you carried.

The other APRs printed on the same card

A card does not have one APR; it has a family of them, and the differences matter. The introductory APR is a promotional rate — often 0% — for a stated number of months on purchases, balance transfers, or both; when it ends, the regular rate applies to whatever is left. The balance transfer APR prices debt moved from another card and usually carries a transfer fee of 3% to 5% of the amount moved — $90 to $150 on a $3,000 transfer — charged upfront even when the rate itself is 0%. Beware the retail variant, deferred interest: on many store-card promotions, missing the payoff deadline makes all the interest that would have accrued from the purchase date come due at once.

The penalty APR is the family’s enforcer — commonly set near 29.99%. Under Regulation Z an issuer generally cannot apply it to existing balances until you are more than 60 days behind, must give 45 days’ notice of a rate increase, and must restore the standard rate on those balances after six consecutive on-time minimum payments. A penalty rate can apply to new purchases sooner than to old balances, which is one more reason a card in penalty territory should be paid, not used.

Cash advances: the APR with no grace period

The cash advance is the most expensive money on the card, for three stacked reasons. It carries its own, higher APR. It has no grace period — interest starts the day the cash comes out. And it charges a fee on top, before any interest at all. A cash advance apr calculator therefore has to add three numbers, not one. Worked on round, illustrative terms: a $500 advance with a 5% fee ($25) at a 29.99% cash advance APR costs $12.32 of interest in the first 30 days — a total of $37.32 for one month’s use of $500, even if it is repaid in full on day 30. Leave it standing and the daily rate keeps working at the highest APR on the card.

Why your card’s APR moves

Most card APRs are variable: a published index, usually the prime rate, plus a margin set when you applied. When the Federal Reserve’s decisions move the prime rate, your APR moves with it — the rate on an existing card can rise without anything about your behaviour changing. A fixed APR does not track an index, but the name overpromises: the issuer can still change it with advance notice. Either way, the rate printed when you applied is a starting point, and the rate in this month’s statement is the one your balance is actually paying.

Sources and method: interest by the daily periodic rate (APR ÷ 365 applied to the average daily balance), the common card method; minimum payment modelled as interest plus 1% of the balance, a common issuer formula, labelled where used. Penalty-APR and notice rules per Regulation Z §1026.55 (CFPB). All rates in the worked examples are round and illustrative; no issuer is named.