Money guide · Credit scores and debt payoff
How credit card interest works: APR and daily balances
Estimate credit card interest using APR, daily balances, and the number of days in a billing period.
How it works
Purchases, cash advances, and transfers can have different rates and terms. A purchase grace period, when available and maintained under the agreement, can allow interest avoidance by paying the statement balance in full. Cash advances often have different rules. Read the agreement and statement rather than assuming every balance gets the same treatment.
A worked example
Using a simplified 365-day method, a 24% APR gives a daily rate of 0.24 / 365. A constant $2,000 balance for 30 days produces about $39.45 in interest: $2,000 × 0.24 / 365 × 30. This illustration excludes daily compounding, transaction changes, fees, and grace-period effects. The issuer’s actual calculation can differ.
What to compare
List the APR for each balance category, any promotional expiration, and how payments are applied. The statement’s minimum payment is the required amount, not a schedule designed to minimize interest. Payments earlier in a billing cycle may reduce balances used in the calculation when interest is accruing. Keep enough cash for other essential obligations.
A common mistake to avoid
Dividing APR by 12 and applying it to the last balance may be a rough estimate but can miss daily changes. Do not assume a 0% promotion makes borrowing free indefinitely; fees and the later rate matter. Deferred-interest arrangements also differ from ordinary introductory APR offers and need their own contract review.
Does paying the minimum avoid interest?
Generally it satisfies the minimum obligation but does not eliminate interest on a carried balance. Grace-period conditions and promotional terms determine exceptions.
Sources and further reading
Connect this to inflation
Inflation changes the spending power of money over time. Read the related inflation explainer, or measure changes in buying power using your own assumptions.