Credit Card Interest Calculator
The Credit Card Interest Calculator shows how much a card balance grows when no payment is made, with interest compounding monthly at your APR.
What this means
Card interest compounds monthly (often daily) on the outstanding balance. Carrying a balance month to month means each month's interest is added to the amount that next month's interest is charged on.
How we calculate it
Formula
Balance after n months = P × (1 + r)^n — with P balance, r monthly rate (APR ÷ 12), n months.Worked example
A $5,000 balance at 20% APR with no payments for 12 months:
- 1Monthly rate = 20% / 12 = 1.667%
- 2Balance after 12 months ≈ $6,095
- 3Interest accrued ≈ $1,095
Important assumptions
- No payments or new purchases are made.
- Interest compounds monthly at the stated APR.
Frequently asked questions
Do cards compound interest daily or monthly?
Most cards calculate interest daily from your daily balance but charge it monthly. Daily compounding grows the balance slightly faster than monthly.
How do I avoid card interest entirely?
Pay your statement balance in full every month before the due date. Most cards then charge no interest on purchases.