The interest on a 3,000 balance
At 22.9% APR, a balance of 3,000 accrues 57.25 in interest in the first month. Paying 100 a month clears it in 45 months — three years and nine months — and costs 1,495.48 in interest, so the card costs 4,495.48 altogether. Paying 150 clears it in 26 months for 814.94 of interest. The extra 50 a month is not 50% more repayment: it is a much larger share of each payment reaching the balance rather than the interest.
Month by month
| 1 | $100.00 | $57.25 | $42.75 | $2,957.25 |
| 2 | $100.00 | $56.43 | $43.57 | $2,913.68 |
| 3 | $100.00 | $55.60 | $44.40 | $2,869.28 |
| 4 | $100.00 | $54.76 | $45.24 | $2,824.04 |
| 5 | $100.00 | $53.89 | $46.11 | $2,777.93 |
| 6 | $100.00 | $53.01 | $46.99 | $2,730.94 |
| 7 | $100.00 | $52.12 | $47.88 | $2,683.06 |
| 8 | $100.00 | $51.20 | $48.80 | $2,634.26 |
| 9 | $100.00 | $50.27 | $49.73 | $2,584.53 |
| 10 | $100.00 | $49.32 | $50.68 | $2,533.85 |
| 11 | $100.00 | $48.35 | $51.65 | $2,482.20 |
| 12 | $100.00 | $47.37 | $52.63 | $2,429.57 |
An estimate, not financial advice. Figures are illustrative and depend on assumptions listed below. Check anything you plan to act on with a qualified adviser or the provider itself.
The worked example below, drawn. A fixed payment is a straight-ish line down; a percentage minimum is a curve that flattens out.
The first month's interest decides everything. A payment below it means the balance grows and no schedule exists.
Raising the payment by half cuts the interest by nearly half, because it shortens the time the debt exists.
Interest accrues daily on most cards, so paying earlier in the cycle helps slightly. This tool computes monthly, as a statement does.
How it works
The formula
Each month, in this order:
interest = round(balance x apr / 100 / 12)
due = balance + interest
payment = round(what you pay this month)
principal = payment - interest
balance = due - payment
On a fixed payment:
payment = the same amount every month
On the minimum:
payment = max(balance x percent + interest, floor)
The last payment is only what is left, so the
totals reconcile with the schedule.
round = to the nearest minor unit, half up.
What it assumes
- Interest is charged monthly at the APR divided by twelve, which is what a statement shows. Most issuers accrue daily, which differs by a small amount over a multi-year payoff and cannot be reconciled against a statement.
- Nothing further is charged to the card. A single new purchase changes every row below it, and is the commonest reason a real balance does not follow a schedule like this one.
- The minimum is modelled as a percentage of the balance plus that month's interest, floored at a fixed amount. That is a common shape and not a universal one — some issuers use a percentage of the balance alone, and the terms vary by card and by country. Both figures are editable.
- There is no promotional rate, no balance transfer, no fee and no missed payment. Each of those changes the answer materially.
- A payment that does not cover the first month of interest is refused rather than reported, because there is no payoff to report. The balance grows for ever.
- The figures carry no currency symbol on purpose. The arithmetic is the same in pounds, euros or dollars, and the tool follows whichever currency your locale uses.
Common questions
Does the APR mean I pay that much in a year?
Not exactly. The APR is an annual figure converted to a monthly rate for statements, and because interest compounds monthly the effective annual cost is a little higher than the headline — 22.9% nominal compounds to about 25.5%. It also assumes the balance stays put, which it does not if you are paying it down.
What about a 0% balance transfer?
It changes the arithmetic entirely and is not modelled here. A transfer typically charges a fee of a few per cent up front and then no interest for a fixed window, so the whole payment reaches the balance during it. The trap is the reversion rate at the end of the window, and a balance that has not cleared by then.
Sources
Method written and checked by Tessalor on Jul 31, 2026.
The full method, worked example and every assumption behind this figure are on Credit Card Payoff Calculator.