Estimate one billing cycle of interest from an average daily balance and disclosed day-count convention.
The calculator keeps the balance, rate convention, payment timing, fees, and term visible so you can reproduce the result and compare it with an actual offer or statement.
Balance / proceedscash charge or interestTime / limit basisExplicit rate or finance chargeInterest = average daily balance × annual rate ÷ day-count basis × billing-cycle days.
Read the result in context
Use the estimate with its contract assumptions
An average daily balance of 1,000 at 18% for 30 days on a 365-day basis produces about 14.79 of interest.
This is an average-daily-balance estimate without within-cycle interest compounding. Issuers may use 360 or 365 days, multiple balances and rates, grace periods, minimum charges, daily compounding, and different transaction timing.
Quick guide
How to use this calculator
Enter the balances, rates, fees, and timing requested by the visible labels.
Keep monetary entries in one consistent currency.
Review the result together with the declared calculation convention and exclusions.
Entered fixed decimals are aggregated exactly. Iterative rate solving is bounded to a single nonnegative monthly cash-flow root and fails explicitly if the result is absent, too large, or not reliably representable.
Worked example
Worked example
An average daily balance of 1,000 at 18% for 30 days on a 365-day basis produces about 14.79 of interest.
Amounts are capped at 1e12, rates at 1000%, monthly periods at 1,200, and fixed decimals at 12 places. List tools accept 1–20 uniquely named rows.
Estimate, not a disclosure
Results model only the entered convention. They do not reproduce a lender statement, credit score, underwriting outcome, or jurisdiction-specific consumer-credit disclosure.
International scope
No currency, country, credit bureau, scoring model, statutory APR rule, fee classification, grace period, or issuer policy is assumed.
Calculator-specific assumptions
This is an average-daily-balance estimate without within-cycle interest compounding. Issuers may use 360 or 365 days, multiple balances and rates, grace periods, minimum charges, daily compounding, and different transaction timing.
