# Credit Card Interest Calculator

URL: https://speedycalculator.com/calculators/finance/credit-card-interest/
Last updated: 2026-10-25

> The credit card interest calculator works out the interest charged on your card for a billing cycle using the average daily balance method, the daily periodic rate, and how much interest you'll pay before the balance is cleared at your monthly payment.

## Inputs

- Average daily balance
- APR (%)
- Days in the billing cycle
- Monthly payment

## Results

- Daily periodic rate
- Interest this billing cycle
- Interest over a year at this balance
- Months to pay off
- Total interest until paid off

## Formula

```
Daily periodic rate = APR ÷ 365
Interest for the cycle = average daily balance × daily rate × days in cycle
Payoff months = nper(APR ÷ 12, payment, balance)
```

## Explanation

Credit card interest compounds daily. If you pay the full statement balance by the due date you pay no interest on purchases thanks to the grace period – carry a balance and you lose it.

### How to use the Credit Card Interest Calculator

- **Average daily balance**
- **APR**
- **Days in the billing cycle**
- **Monthly payment**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the average daily balance, APR, days in the billing cycle and your monthly payment.

### Tips

- Compare loans by APR and total cost, not just the monthly payment.
- Extra payments go straight to principal and can save a lot of interest.
- Pay off the highest-rate debt first if you want to save the most money.
- Check for prepayment penalties before paying a loan off early.

### Common mistakes to avoid

- Stretching a loan term to lower the payment without seeing the extra interest.
- Paying only the minimum on credit cards.
- Forgetting fees that are rolled into the loan.

### Inputs explained

FieldWhat to enterAverage daily balanceAmount in your currencyAPRIn %Days in the billing cycleA numberMonthly paymentAmount in your currency

### What each result means

- **Daily periodic rate** = [APR]÷365
- **Interest this billing cycle** = [Average daily balance]×[APR]÷100÷365×[Days in the billing cycle]
- **Interest over a year at this balance** = [Average daily balance]×((1 + [APR]÷36500)^365 - 1)
- **Months to pay off** = nper([APR]÷1200, [Monthly payment], [Average daily balance])
- **Total interest until paid off** = [Monthly payment]×[Months to pay off] - [Average daily balance]

### Example values

How the main result changes when **Average daily balance** changes and everything else stays at the example values above:

Average daily balanceInterest this billing cycle1,50029.592,25044.383,00059.183,75073.974,50088.776,000118.36

## Worked example

Inputs — Average daily balance: $3,000; APR: 24 %; Days in the billing cycle: 30; Monthly payment: $120.

Results — Daily periodic rate = 0.0658 %; **Interest this billing cycle = $59.18**; Interest over a year at this balance = $813.45; Months to pay off = 35; Total interest until paid off = $1,200.33.

## FAQ

**How do I avoid credit card interest?**
Pay the full statement balance by the due date every month.

**What is the daily periodic rate?**
APR ÷ 365 – the rate applied to each day's balance.

**Does interest compound on credit cards?**
Yes, usually daily.

**What formula does the Credit Card Interest Calculator use?**
Daily periodic rate = APR ÷ 365.


## Sources

- [Consumer Financial Protection Bureau](https://www.consumerfinance.gov/)