Average Daily Balance Calculator
Most interest calculators, including ours, ask for your average daily balance as an input. This tool works it out for you from a starting balance and the purchases and payments that happened during the cycle.
Quick answer: your average daily balance is your balance at the end of every day in the billing cycle, added up and divided by the number of days. Enter your balance at the start of day 1, then add each purchase or payment on the day it actually posted, not the day you made it.
Enter a starting balance and cycle length to see your average daily balance.
Why this isn't just your statement balance
Your statement balance is a snapshot on one day. Your average daily balance accounts for every purchase and payment that happened during the cycle, weighted by how many days each balance was actually outstanding. Paying early in the cycle lowers your average daily balance, and therefore your interest, even if your statement balance ends up the same as if you had paid later.
How the math works
For each day in the billing cycle: start from the prior day's balance, apply anything that posted that day (a purchase increases it, a payment decreases it), and record that day's balance. Add up all the daily balances, then divide by the number of days in the cycle. If you also enter an APR, we estimate interest the same way the rest of this site does: average daily balance × APR ÷ 365 × the number of days in the cycle. See how credit card interest is calculated for the full method, or run a single static balance through the interest calculator if you don't need the day-by-day detail.
Disclaimer. This calculator estimates your average daily balance and, optionally, your interest cost. It does not replace your issuer's own calculation, which may include additional fees, promotional terms, or a different balance computation method disclosed in your cardholder agreement. This is educational information, not financial advice.
Sources: Experian, Forbes Advisor, and Corporate Finance Institute (the average daily balance method and worked examples, independently verified against this calculator's output before publishing).
Frequently asked questions
What is an average daily balance?
It is the balance your card issuer tracks at the end of every day in your billing cycle, added up and divided by the number of days in the cycle. Most issuers use this figure, not your statement balance, to calculate interest.
Should I use the transaction date or the posted date?
Use the day a purchase or payment actually posted to your account, not the day you made it. Purchases usually post the same day. Payments can take a day or more to post, and the balance does not change until it does.
Why does my average daily balance matter?
It is usually the number your issuer multiplies by your daily periodic rate to calculate interest for the cycle, not your current balance or your statement balance. A lower average daily balance means lower interest, which is why paying earlier in the cycle helps.
Does this calculator estimate my interest too?
Yes, if you enter an APR. It applies the same daily-periodic-rate method used throughout this site: your average daily balance times your APR divided by 365, times the number of days in the cycle.