# What is my average daily balance?

Works out a credit card’s average daily balance for a billing cycle (the sum of the daily balances ÷ the days) and the interest at a daily periodic rate of APR ÷ 365.

- Page: https://www.acalculator.org/finance/average-daily-balance-calculator
- JSON spec: https://www.acalculator.org/finance/average-daily-balance-calculator.json
- Version: 2782e5e8b0d2

## Default answer

Example with the default inputs (Balances in the billing cycle [Balance $1,000.00, Days 10; Balance $1,500.00, Days 15; Balance $700.00, Days 5], APR 24%, Days in the year 365): Over 30 days the average daily balance is $1,200.00.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| periods | Balances in the billing cycle | Each balance the account had during the cycle, after that day’s purchases, payments and credits, and for how many days. |
| apr | APR | The card’s annual percentage rate, for the interest. Optional. |
| basis | Days in the year | The daily periodic rate is APR ÷ 365, or APR ÷ 360 for card issuers that use 360 days. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| average | Average daily balance | The sum of the daily balances ÷ the days in the cycle. |
| days | Days in the billing cycle | The days of all the rows added up. |
| sum | Sum of the daily balances | Each balance × its days, added up. |
| dailyRate | Daily periodic rate | APR ÷ 365 (or ÷ 360). Shown when an APR is typed. |
| interest | Interest for the cycle | Average daily balance × days × daily periodic rate ÷ 100. Shown when an APR is typed. |

## Method

Average daily balance = Σ (balance × days) ÷ Σ days. Daily periodic rate = APR ÷ 365 (or ÷ 360). Interest for the cycle = average daily balance × days in the cycle × daily periodic rate ÷ 100.

## Assumptions

- Each balance is the end-of-day balance after that day’s purchases, fees, payments and credits (the method that includes current transactions).
- No compounding within the cycle: the interest is not added to the daily balances.
- Arithmetic is exact on the typed decimals; money shows to the cent, halves rounded up.

## Worked examples

1. periods = {"balance":"1000","days":10} or {"balance":"1500","days":15}, apr = 24%, basis = 365 gives average = $1,200.00, days = 30, sum = $36,000.00, dailyRate = 0.065753%, interest = $23.67. Source: CFPB, Regulation Z (12 CFR part 1026), Appendix G-1(A), clause (d), Average Daily Balance Method (Including Current Transactions), https://www.consumerfinance.gov/rules-policy/regulations/1026/g/; CFPB, Regulation Z, comment 7(b)(5)-4.i.D (average daily balance × days in the cycle × periodic rate), https://www.consumerfinance.gov/rules-policy/regulations/1026/interp-7/.
2. periods = {"balance":"500","days":31} or undefined, apr = 18%, basis = 365 gives average = $500.00, days = 31, interest = $7.64. Source: CFPB, Regulation Z (12 CFR part 1026), Appendix G-1(A), clause (d), Average Daily Balance Method (Including Current Transactions), https://www.consumerfinance.gov/rules-policy/regulations/1026/g/; CFPB, Regulation Z, comment 7(b)(5)-4.i.D (average daily balance × days in the cycle × periodic rate), https://www.consumerfinance.gov/rules-policy/regulations/1026/interp-7/.
3. periods = {"balance":"0","days":12} or {"balance":"2500.5","days":18}, basis = 365 gives average = $1,500.30, days = 30, sum = $45,009.00. Source: CFPB, Regulation Z (12 CFR part 1026), Appendix G-1(A), clause (d), Average Daily Balance Method (Including Current Transactions), https://www.consumerfinance.gov/rules-policy/regulations/1026/g/.
4. periods = {"balance":"1000","days":10} or {"balance":"1500","days":15}, apr = 24%, basis = 360 gives average = $1,200.00, dailyRate = 0.066667%, interest = $24.00. Source: CFPB, Regulation Z, comment 7(b)(5)-4.i.D (average daily balance × days in the cycle × periodic rate), https://www.consumerfinance.gov/rules-policy/regulations/1026/interp-7/.

## FAQ

### What is the average daily balance?

It is the average of the balance at the end of each day of the billing cycle: add up every day’s balance and divide by the number of days. Most credit card issuers charge interest on it.

### How do I calculate the average daily balance?

Multiply each balance by the number of days it lasted, add the results, and divide by the days in the cycle. $1,000 for 10 days, $1,500 for 15 days and $700 for 5 days give 10,000 + 22,500 + 3,500 = 36,000, and 36,000 ÷ 30 = $1,200.

### How is credit card interest figured from it?

Multiply the average daily balance by the number of days in the cycle and by the daily periodic rate, which is the APR divided by 365 (some issuers use 360). At 24% APR, $1,200 for 30 days costs 1,200 × 30 × 0.24 ÷ 365 = $23.67.

### Do new purchases count in the balance?

Under the method most cards use (average daily balance including current transactions), yes: each day’s balance adds that day’s new purchases and fees and subtracts payments and credits. Your card agreement says which method your issuer uses.

### Why does paying early lower my interest?

A payment lowers the balance for every remaining day of the cycle, so the earlier you pay, the more days carry the lower balance and the smaller the average daily balance.

### Do I pay interest if I pay in full every month?

Usually not on purchases: most cards give a grace period, and if you pay the whole statement balance by the due date, no interest is charged on new purchases. Interest on the average daily balance applies when you carry a balance.

## Sources

- Consumer Financial Protection Bureau, Regulation Z (12 CFR part 1026), Appendix G-1(A), clause (d), Average Daily Balance Method (Including Current Transactions): each day’s balance adds new purchases and subtracts payments and credits; the daily balances are added and divided by the number of days in the billing cycle, and the periodic rate is applied to that average. https://www.consumerfinance.gov/rules-policy/regulations/1026/g/ (retrieved 2026-10-19)
- Consumer Financial Protection Bureau, Regulation Z, official interpretation of § 1026.7, comment 7(b)(5)-4.i.D: the average daily balance multiplied by the number of days in the billing cycle and the periodic rate gives the interest. https://www.consumerfinance.gov/rules-policy/regulations/1026/interp-7/ (retrieved 2026-10-19)
- Consumer Financial Protection Bureau, Credit card contract definitions: the daily periodic rate is the APR divided by 365. https://www.consumerfinance.gov/data-research/credit-card-data/know-you-owe-credit-cards/credit-card-contract-definitions/ (retrieved 2026-10-19)
- Consumer Financial Protection Bureau, Ask CFPB, What is a “daily periodic rate” on a credit card?: the APR divided by 360 or 365, depending on the card issuer. https://www.consumerfinance.gov/ask-cfpb/what-is-a-daily-periodic-rate-on-a-credit-card-en-46/ (retrieved 2026-10-19)
- Consumer Financial Protection Bureau, Ask CFPB, How does my credit card company calculate the amount of interest I owe?: many issuers charge interest daily on the average daily balance; paying earlier lowers it; a grace period usually covers new purchases when the full balance is paid by the due date. https://www.consumerfinance.gov/ask-cfpb/how-does-my-credit-card-company-calculate-the-amount-of-interest-i-owe-en-51/ (retrieved 2026-10-19)