how do you calculate apr on a credit card
How your monthly interest charge is calculated. Interest charges are calculated on a monthly basis. Since months vary in length, most credit card issuers use a Daily Periodic Rate (DPR) to calculate interest charges. The DPR is calculated by dividing the APR by 365.ow your monthly interest charge is calculated. Interest charges are calculated on a monthly basis. Since months vary in length, most credit card issuers use a Daily Periodic Rate (DPR) to calculate interest charges. The DPR is calculated by dividing the APR by 365.