Credit Card Interest Calculator
Calculate credit card interest from your own entered figures.
Loading calculator…
Currency: Amounts are calculated in the currency you select; this site does not convert between currencies and does not use live exchange rates.
What this tool does
Calculate credit card interest from your own entered figures. Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.
How to use the Credit Card Interest Calculator
- Enter or select balance carried.
- Enter or select card apr (%).
- Enter or select days in billing cycle.
- Enter or select new purchases per day (optional).
- Read the calculated result; change any measurement to compare alternatives.
Formula
average daily balance method: ADB = balance + daily spend × days/2 when purchases accrue evenly; interest = ADB × (APR/100) × days/365
- balance
- Balance carried
- apr
- Card APR (%)
- days
- Days in billing cycle
- dailySpend
- New purchases per day (optional)
Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.
Worked example
For credit card interest calculator, the following measurements illustrate the exact method: Balance carried: 3000; Card APR (%): 24; Days in billing cycle: 30; New purchases per day (optional): 0.
Inputs
- Balance carried$3000
- Card APR (%)24 %
- Days in billing cycle30
- New purchases per day (optional)$0
Result
- Interest charged this cycle$59.18
- Average daily balance$3,000.00
- Interest per day$1.97
- Year of interest at this pace$720.00
Results explained
- Interest charged this cycle
- Interest charged this cycle from the formula above. Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.
- Average daily balance
- Average daily balance from the formula above. Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.
- Interest per day
- Interest per day from the formula above. Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.
- Year of interest at this pace
- Year of interest at this pace from the formula above. Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.
Frequently asked questions
average daily balance method: ADB = balance + daily spend × days/2 when purchases accrue evenly; interest = ADB × (APR/100) × days/365
Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.
No. All numbers are entered by you or come from the dated reference table shown on this page; calculations run locally.
This is an estimate, not financial, tax or legal advice. Verify the inputs and output with official sources and a qualified professional.
Check period consistency, currency, percentage inputs and the assumptions: Uses the average-daily-balance method most issuers disclose, with purchases spread evenly across the cycle and no grace period (a balance is being carried). Payments during the cycle are not modeled.