Interest-Free Period Calculator
Work out whether you can repay a purchase within a credit card's interest-free period, and the interest you would owe if you fall short.
Your results
Calculation breakdown
- Shortfall
- purchase amount − planned repayment
- Interest if not cleared
- purchase × annual rate × (interest-free days ÷ 365)
Worked example
A $1,500 purchase with 55 interest-free days costs nothing if repaid in full by the due date, but paying only $1,200 could trigger interest on the full $1,500 at the card's rate, often over 20% p.a.
Assumptions
- Assumes interest applies to the full purchase amount if the statement balance is not cleared, as most Australian cards do.
- Interest-free days vary by card and purchase timing within the statement cycle.
- Cash advances typically have no interest-free period; this tool is for purchases.
How this calculator works
Many Australian credit cards offer up to around 55 days interest-free on new purchases if the full balance is paid by the due date. This calculator compares your planned repayment against the purchase amount and interest-free period to show any shortfall and the resulting interest charge if you do not clear the balance in time.
Frequently asked questions
How is the interest-free period usually calculated?
It typically runs from the start of a statement cycle to the payment due date, so the exact interest-free days for a purchase depend on when in the cycle you make it; check your card's terms for the precise rule.
What happens if I only pay part of the balance?
Most cards charge interest on the entire remaining balance from the transaction date, not just the unpaid portion, once you miss paying the statement balance in full, so any shortfall can be costly.
Does this apply to cash advances?
No, cash advances usually accrue interest immediately with no interest-free period, which is different to purchases; check your card's terms for cash advance treatment.
Results are estimates only and are not financial, tax, legal or credit advice.