What is my average daily balance?
Type each balance your card had during the billing cycle and how many days it lasted. The average daily balance calculator adds up the daily balances, divides by the days, and works out the interest at your APR.
- Average daily balance
- $1,200.00
Over 30 days the average daily balance is $1,200.00.
- Days in the billing cycle
- 30
- Sum of the daily balances
- $36,000.00
- Daily periodic rate
- 0.065753%
- Interest for the cycle
- $23.67
Average daily balance: $1,200.00. Over 30 days the average daily balance is $1,200.00.
The results are estimates for information only. They are not financial, tax, or legal advice. Check the numbers with your lender or a qualified professional before you decide. Terms of use
How to calculate
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.
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.
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.
- 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
Each example is checked against the calculator on every build.
- Balances in the billing cycle 1000 10; 1500 15; 700 5, APR 24%, Days in the year 365 gives Average daily balance $1,200.00, Days in the billing cycle 30, Sum of the daily balances $36,000.00, Daily periodic rate 0.065753%, Interest for the cycle $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/
- Balances in the billing cycle 500 31, APR 18%, Days in the year 365 gives Average daily balance $500.00, Days in the billing cycle 31, Interest for the cycle $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/
- Balances in the billing cycle 0 12; 2500.5 18, Days in the year 365 gives Average daily balance $1,500.30, Days in the billing cycle 30, Sum of the daily balances $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/
- Balances in the billing cycle 1000 10; 1500 15; 700 5, APR 24%, Days in the year 360 gives Average daily balance $1,200.00, Daily periodic rate 0.066667%, Interest for the cycle $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/
How it works
Each row is a balance and the number of days the account ended the day at that balance.
- Sum of the daily balances = Σ (balance × days), over the rows.
- Days in the billing cycle = Σ days.
- Average daily balance = sum of the daily balances ÷ days in the billing cycle.
- Daily periodic rate = APR ÷ 365, or APR ÷ 360 when that choice is made (shown as a percent).
- Interest for the cycle = average daily balance × days in the billing cycle × daily periodic rate ÷ 100.
The daily periodic rate and the interest show only when an APR is typed.
Rules:
- 1 to 31 rows. Each balance is $0 to $1,000,000,000; each row is 1 to 366 whole days. The APR is 0% to 100%.
- Days that add up to more than 366 give no answer: "The days add up to more than 366: a billing cycle is at most a year."
- A result that is not $0 but is too small to show as a number (under about 2.5 × 10⁻³²⁴, which only amounts typed far below a cent can give) gives no answer: "A result is too small to show as a number." Nothing is too large to show within these limits.
- The arithmetic is exact on the decimals you type. Money shows to the cent and the daily rate to at most 6 decimals (trailing zeros dropped), with halves rounded up (away from zero), from the exact value.
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: interest is not added to the daily balances. A card that compounds daily charges slightly more.
- One APR for the whole balance. When purchases and cash advances have different rates, work out each balance separately.
Worked examples by hand
A 30-day cycle. $1,000 for 10 days, then $1,500 for 15 days after a $500 purchase, then $700 for 5 days after an $800 payment. Sum = 1,000 × 10 + 1,500 × 15 + 700 × 5 = $36,000; days = 30; average daily balance = 36,000 ÷ 30 = $1,200. At 24% APR: daily rate = 24 ÷ 365 = 0.065753%; interest = 1,200 × 30 × 0.24 ÷ 365 = $23.67 (23.6712…). With a 360-day year: daily rate 0.066667%, interest = 1,200 × 30 × 0.24 ÷ 360 = $24.00.
A balance that does not change. $500 for all 31 days: average daily balance $500; at 18% APR, interest = 500 × 31 × 0.18 ÷ 365 = $7.64 (7.6438…).
A purchase partway through. $0 for 12 days, then $2,500.50 for 18 days: sum = 2,500.50 × 18 = $45,009; average daily balance = 45,009 ÷ 30 = $1,500.30.
Other questions people ask
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.