Free · No ads · No login
Credit card interest calculator
What does paying only the minimum really cost? See how long your card takes to clear, the interest it adds, and how much sooner a fixed amount each month gets you out.
20.95% is an example, common on standard cards. Your statement shows yours.
Assumes you stop using the card and nothing else is added. Fees, promotional rates and cash advances aren't included.
Enter your card balance to see what paying only the minimum really costs. For example, $3,000 at 20.95% on a 3% or $10 minimum takes 18 years 2 months and $3,735 in interest.
Pure arithmetic on the numbers you enter · last reviewed October 2026.
Free, no ads, and it runs in your browser: what you type isn't sent to us unless you choose to share or save a result. Spotted a mistake? Let us know.
How credit card interest works
A credit card charges interest on whatever you haven't paid off. It's worked out daily and added monthly, so a balance that sits there grows a little every day.
The minimum payment is set to keep your account in good standing, not to clear the debt. Because it's a percentage of a shrinking balance, it shrinks too, and paying only the minimum can stretch a few thousand dollars over more than a decade.
Two things make the biggest difference:
- A fixed amount each month, even a modest one, that stays the same as the balance falls.
- Paying the full statement balance once the debt is gone, so you keep your interest-free days on new purchases.
Credit card questions, answered
- How is credit card interest worked out in NZ?
- Most cards work out interest every day on what you owe, at the card's purchase rate divided by 365, and add it to your balance once a month. On a $3,000 balance at 20.95% that's about $1.72 a day, or roughly $52 a month, before you've bought anything new.
- Why does paying the minimum take so long?
- The minimum is a small slice of the balance, often 3% or $10, whichever is higher. In the early months most of that slice goes on interest, so the balance barely moves. And as the balance shrinks, so does the minimum, which stretches the tail out for years. A fixed amount that doesn't shrink is what breaks the cycle.
- What are interest-free days, and how do I lose them?
- Many cards give you up to about 44 to 55 days without interest on purchases, but only if you pay the full closing balance by the due date. Carry any balance over and most cards charge interest on new purchases from the day you make them, as well as on what you already owed. Check your card's terms for exactly how yours works.
- What about cash advances?
- Taking cash out on a credit card usually costs more: a higher interest rate, no interest-free days, and often a fee. This calculator uses your purchase rate, so it doesn't cover cash advances.
- I have more than one debt. What should I pay first?
- Pay the minimum on everything, then put every spare dollar on one debt at a time. Our debt payoff calculator compares the two common orders (highest interest first, or smallest balance first) and shows your debt-free date.
- I'm struggling with repayments. Where can I get help?
- Talk to your bank early: they can sometimes help with a hardship arrangement. MoneyTalks is a free, confidential financial helpline: call 0800 345 123, text 4029, or chat at moneytalks.co.nz. They can also connect you with free financial mentors near you.
- Is my data stored anywhere?
- No. It all runs in your browser. The only thing that touches our servers is the URL you create with 'Copy share link', which contains just the numbers you entered.
Find the money for a bigger payment.
KeaBudget shows what's safe to spend until payday, after your bills, so you can see how much more you could put on the card each month. It's free.
Start using KeaBudget →More free tools
Debt Payoff Calculator →Emergency Fund Calculator →NZ Take-home Pay Calculator →Related reading: How to budget in New Zealand: a simple guide. Or see all our free NZ money calculators.